Browser JavaScript

Browser JavaScript Explained

Browser JavaScript is a feature that allows Opera to automatically fix incompatible Web pages, out of date scripts, and pages that inadvertently block Opera. The script file is automatically distributed by Opera Software ASA, and can be used to apply fixes to specific Web sites, and specific scripts.

Browser JavaScript respects your JavaScript preferences, and will not be loaded if JavaScript is disabled.

Current browser.js status: checking... How do I enable it?

Note: Opera also provides User JavaScript, which allows you to apply your own enhancements and fixes to Web pages. Additionally, Opera Software ASA runs the Open the Web initiative, which contacts the authors of problematic Web sites.

Keeping up-to-date

Opera automatically checks for updates to Browser JavaScript once every week. Any updates will be automatically downloaded and applied the next time a page is loaded in Opera.
Automatic checking is controlled by the Browser JavaScript and Check For New Opera settings in Opera6.ini.
Files are downloaded separately for each user of Opera, and you do not have to be an administrator of your computer to make use of this feature.
The Browser JavaScript is signed and distributed by Opera Software ASA, and should not be edited.
The file will be stored in Opera's profile folder. The Help > About screen will tell you where the profile folder is.

If you use a proxy server that requires user name and password to access the internet, please note that Opera will not request user name and password for an authenticating proxy in order to download site patches. Site patching or upgrade notification may not take place if such proxies are required, but you may be able to check for updates manually.

Enabling browser.js

If you have changed settings, or changed the file itself, the browser.js feature may have become disabled.

Go to the Browser JavaScript setting and change the value to 2.
Click the "Save" button below the setting.
Re-load this page and check if the status message at the top says browser.js is enabled.

If this doesn't work for you, the file may be corrupted. Please follow the instructions on "checking for updates manually" in the next section.

Checking for updates manually

Opera downloads the file automatically once a week, but if you want to make absolutely sure you have the latest file you can follow these steps:

Go to the Browser JavaScript setting and change the value to 1.
Click the "Save" button below the setting.
Use Help > Check for updates in Opera's menu bar.

Opera may tell you no new Opera version is available, but it will still check for a new version of the browser.js file.

Patches applied by Browser JavaScript

In most cases, when Browser JavaScript applies a fix, a message is posted in the JavaScript console (Tools > Advanced > JavaScript console) saying that the page has been changed.

Please note: Some of the fixes apply to specific Opera versions, or on specific platforms only.

Site fixes

saab

sniffing on saab.com and saab.de excludes Opera

www.opera.com

Browser.js status and version reported on browser.js documentation page

bbc.co.uk

Mobile BBC should default to mobile view

fileplanet.com

Fileplanet.com sniffing blocks Opera

nmviewogc.cr.usgs.gov

National Map Viewer on USGS relies on Netscape detection for functionality

windowsmedia.com

Mobile Windowsmedia site does not trigger mobile view

americanexpress

AmericanExpress blurs form elements on click

amazon

Workaround for a layout bug in opera that only affects older versions, causing the search field on amazon.com and amazon.de to becoe 3 pixels wide.

cang.baidu.com

cang.baidu.com for Baidu SouCang can't display saved items

epa.qld.gov.au

epa.qld.gov.au site uses capturing load events.

lotteimall.com

fixes a spurious alert on lotteimall.com

slashdot.org

Removes large focus areas covering the article area and the columns to the right on slashdot.org

tianya.cn

Fix missing scrollbars and misplaced text.

aaa.com

Sniffing on aaa.com prevents zip code search

anz.com

ANZ online bank form action URLs are incorrectly decoded

aol

dell

browser sniffing on support.dell.com

dfdsseaways

DFDS calendar is 1900 years in the future

ebay

eBay: can not upload images
eBay: speed up back+forward navigation
Cannot use ebay.com dropdown with virtual pointer
Remove global click listeners for mini on ebay
ebay.fr hangs, Opera doesn't support option node passed to SELECT.remove()
eBay re-type validation depends on keypress event support

ems.com.cn

Menus on ems.com.cn disappear too quickly

google

Google calendar date selection fails due to order of blur and mousedown events
Google Reader wraps long feed titles
V shortcut in Google reader opens blank page
Google codesearch results source code rendered white-on-white
Google navigation bar overlaps if localised text is too long

hp.com

HP shopping site is designed for smaller fonts

ibm.com

IBM driver download has HTML comments inside SCRIPT tag, breaks parsing

icicibank

ICICI online bank form action URLs are incorrectly decoded

ogame.org

Ogame.org layout issue

scandinavian.net

Selects are reset if first option is removed in onchange

sony

UDM on sony.com breaks if insertRule throws exceptions

t-online.de

video problems on T-online.de
video problems on T-online.de, VOD section
video problems on T-online.de, WMP license installation
video problems on T-online.de, no window.external detection

tom.com

document.write() overwrites document on tom.com

ulead

Ulead.com old Milonic menu

yahoo

Yahoo!

able.co.jp

able.co.jp uses capturing event listeners

addynamix.com

Fixes panning on addynamix.com

allabout.co.jp

Works around script scheduling bug on AllAbout

allegro.pl

Fix randomly ocurring script scheduling freeze on allegro.pl

amazon.com.cn

Menus on amazon.com.cn disappear too quickly

ameba.jp

Handle popup submit for products where popups are a bad idea
Enable blog post editor on ameba.jp
Work around Opera bug where second BR tag overwrites newly inserted IMG
Show the "tags only" editor, which is the only supported one

anycall.com

Hide popup ad that can't be closed and blocks most content on the site

apple.com

Apple.com is written for higher resolutions than a TV

apple.viamichelin.com

Text on Apple store locator page is misaligned and overlapping

att.com

Browser sniffing causes failed Flash detection
ATT / Bellsouth browser sniffing

barnesandnoble.com

Barnes&Noble uses "required" attributes on elements that aren't required

bbs.kafan.cn

Setting innerHTML to badly nested markup breaks forum layout on bbs.kafan.cn

bbs.pcpop.com

Page loads blank due to misnested forms

bcbssc.com

Blue Cross SC looks up named elements with getElementById()

belastingdienst.nl

enabling an alternate stylesheet while it is still loading is ignored

betfair.com

Betfair relies on firstChild defined on attribute nodes

bhaskar.com

TATA: Align text in cells to left in SSR Mode

bioware.com

bioware.com uses outdated HierMenus

blogger.com

Blogger: browser detection prevents WYSIWYG editing
Blogger: Should distinguish AltGr and Ctrl

bnz.co.nz

bnz.co.nz use getYear when they should use getFullYear

bookryanair.com

Make Opera's built-in WF2 validation ignore required attributes on bookryanair.com

britannica.com

Prevent overwriting document with stats graphic on britannica.com

britishairways

Prevent britishairways.com from reloading the page on resize
britishairways.com hides calendar behind IFRAME
Makes calendar work in spite of unexpected order of mouse events

budget.com

Budget.com: menu appears behind IFRAME "shim"

buienradar.nl

Fix positioning after clicking map on buienradar.nl

cajamadrid.es

Caja Madrid hides login form by CSS mistake

capitalone.com

CapitalOne login fails - cross-domain access on https disallows setting location

cdec-sic.cl

Old HierMenus on cdec-sic.cl

cdon

Shopping cart not displayed

chaseonline.chase.com

chase.com field refocus from onkeypress-problem

cheaptickets.com

Cheaptickets new Function() issue workaround

china-pub.com

Work around window.event getter bug

chinatimes.com

Prevent unexpected back navigation on chinatimes.com

chosun.com

Morningplus.chosun.com misplaced content

clearwire.com

PIONER-268 Flash on clearwire.com doesn't display on homepage

continental.com

Continental.com document.activeElement fix enables airport choice popup

cs.kddi.com

Prevent KDDI site's "anti-multiple-tabs" script from closing window randomly

danawa.com

Iframe content height is too small and not expanded on danawa.com

dancenter.com

Dancenter use getYear when they should use getFullYear

dcf-access.dcf.state.fl.us

Access Florida invalid markup problem

dcinside.com

Fixes having scrollbars appear when panning on dcinside.com

deviantart.com

deviantart.com prevents mousedown on file inputs, making it impossible to select files
Work around bug that breaks Deviantart categories menu

digg.com

script scheduling trouble on digg.com

diodeo.com

Offsets a very noticeable image in the header of diodeo.com

docs.google

Can't select text in Google PDF viewer

docs.google.com

Google Docs : Redirecting to mobile version

douane.nl

enabling an alternate stylesheet while it is still loading is ignored

drudgereport.com

Font-related fix for drudgereport.com

elkjop.no

Elkjop UI breaks on Nintendo Wii because select-multiple by default doesn't un-select other options on click

ent.sina.com.cn

Wrapping content in NewStars section

enter.nifmail.jp

Nifmail web mail bypass browser blocking

espn.go.com

espn.go.com: fix search box overlap

facebook.com

Facebook: Enable posting to discussion groups
Facebook.com: search for groups
Facebook: fix comment forms
Facebook.com: disable "presence" bar

fedex.com

FedEx.com mangles tables by turning TDs into block elements

forbes.com

Forbes layout ruined because linked stylesheets in body are ignored after DOM manipulation
chained loading tries to use both onreadystatechange and onload, only one of them is required
<table><form><tr> is invalid, element->form associations are not kept during DOM changes

foxnews.com

Foxnews.com: Fix captions

geoaccess.com

BlueCross browser sniffing prevents insurance search

grainger.com

ignore document.onload on grainger.com

groups.google

Opera's interpretation of 100% height isn't high enough for Google Groups

gucci.com

gucci.com start page fails to appear on small screens due to typo in script

ibank.isb.ru

browser sniffing breaks ibank.isb.ru

icelandair

jQuery script scheduling trouble on Icelandair

icicidirect.com

styling INPUT with text-transform can confuse users

ingdirect.com.au

Make Opera's built-in WF2 validation ignore required attributes on ingdirect.com.au
ING Direct login issues

iple.com

Blocks floating flash ad on iple.com

irishferries.com

Unexpected text nodes in document.all breaks booking

ironmaiden.com

fix disappearing menu on ironmaiden.com

isbank.com.tr

fixing navigation menu on isbank.com.tr
Preventing CSS filter errors on isbank.com.tr
fixing keypress handler on isbank.com.tr

klm.com

KLM uses Gecko-specific originalTarget

kr.msn.com

head layout broken on kr.msn.com

kubuntu.org

Nested z-index hides content

lgmobile.com

LG Mobile Flash does not load as expected because of missing type attribute

m.reference.com

Mobile reference.com uses generic doctype

m.zdnet.com

Mobile zdnet.com should be displayed in mobile view

mail.163.com

Default to simple html version on mail.163.com
Fix for hidden overflow text on 163.com

mail.google

GMail deletes messages on End key presses
GMail chat: Can not go "off record" (Opera bug workaround)
GMail chat: A link to "#" in a JS-generated document must not cause a re-load
GMail: prevent navigation menu on the left in RTL interface

mail.google.com

GMail detects mobile version as desktop version if opera.version() says 9.5
Hides supported browser complaint in header of mail.google.com

mail.live.com

Fix drag and drop in Hotmail
define document.selection.empty in Hotmail (part of drag-and-drop fix)
Mispositioned sprites due to missing CSS
Detecting style.filter causes missing opacity effects
Borders on folders remain after dragging things past them
Defining a setter causes difference between point and bracket notation for ES properties, breaks panel resize
Handle setting style.left/top to null
Opera doesn't support col-resize/row-resize cursors.
Identify as Opera to the client-side sniffer
Correct browser detection cookie
Ensure a font with bold/italic variants is default for editor on Mac
Fixes downloading attachments in Hotmail
Emulating IE's cssText property on style sheets
Fake designMode for Hotmail, hides rich text UI
Hotmail: enable scrolling of BODY
To-button does not bring up contacts list
Fake getters/setters support
Work around browser warning
Fixes downloading attachments in Hotmail for O10.
Fake oncontextmenu support on Hotmail
Hotmail uses lookupGetter on prototypes, not instances
It's usually not necessary to define properties that are already supported with getters and setters.
Resize function causes rendering loop
redefine document.selection with live.com's compat-layer version
Adding editor area styling that is missing due to browser sniffing

mail.yahoo.com

Disable Rich text editor on mail.yahoo.com

makemytrip.com

MakeMyTrip search fails
MakeMyTrip search fails

mapion.co.jp

Missing whitespace between links expands table on mapion.co.jp

maps.bing.com

Loading Atlas libraries depends on immediate load events for scripts

maps.google

XMLHttpRequests sometimes get stuck if script was in cache
Enable alt-click to show context menu in map
avoid horizontal scrolling on maps.google.com
Google maps eval callback

maps.ubiest.com

Ubiest.com uses CSS filters if document.all exists

marktplaats.nl

Can't add article to favourites because setting link.search has no effect

maserati.com

Allow access to whole page on maserati.com

mb.softbank.jp

Softbank shop uses reserved variable name parent

mcafee.com

McAfee.com menu requires navigator.appName to be Netscape

microsoft.com

Layout fix for microsoft.com

millenet.pl

Semicolon insertion fails after do..while() conditional

mixi.jp

Mixi.jp: correct layout

mk.co.kr

mk.co.kr requests a lot of additional javascript after checking document.all - customer requested fix for load time

mobile.answers.com

Mobile answers.com displayed as desktop site

mobile.handango.com

mobile.handango.com pages are displayed in overview mode, since they are declared without doctype.

mobile.microsoft.com

Mobile microsoft.com should be displayed as a mobile page

mobile.orange.ch

Fix for table align making tables behave as inline on mobile.orange.ch

mobile.youporn.com

Mobile youporn.com uses generic doctype

moneta.co.kr

Renames method on moneta.co.kr (was named goto), also hides flash advertisements that cover content
moneta.co.kr relies on IE quirks for CSS positioning
Gets rid of flash that is mispositioned on moneta.co.kr
Hides background image in search bar on moneta.co.kr

monster

Monster category tree broken by their selectNodes function overwriting .text on nodes

msnbc.com

MSNBC sniffing hides Flash content

n-gage.com

N-Gage plugin sniffing does not give Flash to Mac Opera

namooya.com

Namooya.com main flash does not appear

nasdaq.com

Fix Nasdaq overlapping content

nba.com

load event not triggered when expected in video section

nbc4.tv

NBC4.tv uses capturing load events

nbcolympics.com

NBC Olympics site uses capturing load events

nectar.com

Nectar uses getYear where they should use getFullYear

netian.com

Moves the absolutely positioned SMS div on netian.com (after logging in)

netlog.com

netlog.com: Remove site chat/presence bar

netpia.linkprice.com

Clears popups that are visible after loading subpages on netpia.linkprice.com

news.bbc.co.uk

Fix footer menu on news.bbc.co.uk

news.msn.co.kr

news.msn.co.kr navigation bar is offset from the page

news.qq.com

Requires add() method on SELECT elements
weather.news.qq.com expects getElementById() to find named elements
weather.news.qq.com uses document.all for browser detection
qq.com uses IE-style CSS filters

news.sina.com.cn

Unexpected CDATA escape breaks JS parsing

nick.com

Nick.com flash detection fix

nrg.co.il

NRG.co.il saving articles does not work

o2active

o2active.de, making sure narrow centered column does not appear off-screen

orbitz.com

Orbitz new Function() issue workaround

orkut.com

can't change orkut avatar picture
orkut avatar image crop does not happen because of timing issue
Fix for uploading pictures on orkut.com
Fix iframe width on orkut.com

ota.getvzappzone.com

Verizon Wireless mobile app zone site should default to mobile view

pda.naver.com

pda.naver.com appears half-offscreen

photobucket.com

Photobucket menus disappear too quickly

pluginfree.com

DNP Pluginfree Viewer fallback to Netscape version for Opera

poczta.onet.pl

poczta.onet.pl RTE broken in 9.50

pogo.com

Java detection fails on pogo.com
Loading problems on pogo.com because of document.load in frameset event handler scope

portalaz.com.br

fix disappearing menu on portalaz.com.br

prisjakt.nu

prisjakt.nu capturing load events on back navigation

qzone.qq.com

Browser sniffing during login makes site expect Opera's old script loading implementation on qq.com

rabobank.nl

Rabobank cancels t keypress

redfin.com

Solve Dojo script scheduling trouble on redfin.com

rent.toyota.co.jp

Set window.open's default URL to about:blank on rent.toyota.co.jp

rr.com

Text-shadow not properly specified on rr.com

sabadellatlantico.com

SabadellAtlantico use getYear when they should use getFullYear

salesforce.com

Downloading documents on salesforce.com runs into too strict anti-drive-by-install security
Salesforce runs into HTML5's data looking for window.data

samsungmobileusa.com

Samsung USA flash detection fix

sayclub.com

hides id and password background images that are text input backgrounds

seb-bank.de

SEB bank prevents typing certain keys

sfc.jp

noscript content shows on sfc.jp

sfile.ydy.com

Avoid manipulating broken Discuz! markup on sfile.ydy.com

shoptime.com.br

Fix for not possible to type since Opera does not support charCode

show.co.kr

Pre-filled text as INPUT background not cleared on focus

shutterfly.com

Array splice throws on 0-length arrays, breaks Shutterfly.com

sina.com.cn

Layout fix for Sina.com.cn

siren24.com

ActiveX installation page redirect on siren24.com due to sniffing limitation on redirect script

sogou.com

Sogou.com uses window.MouseEvent
hide SVG's style.filter property from script on map.sogou.com because it thinks we are IE

spaces.live.com

Overriding spaces.live.com browser sniffing
Make Range.prototype.insertNode automatically import nodes from other documents

sperrysoftware.com

Nested tables with 100% height are not laid out as expected, menu is pushed down

sports.donga.com

Blocks floating flash ad on sports.donga.com that cannot be closed

star.moneytoday.co.kr

Clicks on a link to display the front page story in an iframe on star.moneytoday.co.kr

status.xiaonei.com

Allow the comments to be visible

sun.com

Menu entries off-screen on sun.com due to font size

surveymonkey.com

Layout fix for surveymonkey.com

sytadin.fr

Sytadin.fr IFRAME resize script detects Opera

tam.com.br

Fixing TAM form element reference issue

taobao.com

Fix Taobao search layout overlap issue

tdwaterhouse.ca

tdwaterhouse.ca login fails - cross-domain access on https disallows setting location

teletekst.nos.nl

Teletext focus fix

tickets.com

Scripts are not allowed to use reserved identifier "top"

time.com

time.com script causes reload loop if UA contains "Windows CE"

tiscali.it

Allows some frame nesting on web.tiscali.it

tistory.com

two login buttons on tistory.com

toeslagen.nl

enabling an alternate stylesheet while it is still loading is ignored

trafikanten.no

Trafikanten.no: Unclickable wrapped menu below frame fold

tudou.com

tudou login doesn't work because it expects input type=button to support .checked

tuenti.com

Problems submitting messages and comments on tuenti.com
Tuenti.com thinks images are not loaded if we don't send them a load event. This only happens to visible images.

unicaja.es

unicaja.es cannot use reserved frame reference words as variables

united.com

United.com flight search problem: hidden images do not load, so no onload event

us.etrade.com

Working around E*Trade site's security policy violation

usairways.com

USAirways is not compatible with WF2 spec required attribute

usatoday.com

Work around browser sniffing to make videos appear

veoh.com

Prevent Omniture-overwritten documents on veoh.com

vgtv.no

Work around browser sniffing for Move media player

viacom.com

Tweaked SWFObject on viacom.com creates constant document reflows

viddler.com

Prevent re-execution of scripts on viddler.com

video.nbc.com

NBC.com video problems

vkontakte.ru

Fix for updating status on vkontakte.ru
Enables searching for people on vkontakte.ru

wachovia.com

Viewing checks calls createElement with markup strings if document.all exists

walla.co.il

Walla.co.il odd CSS styling causes display problems. Bugs 184398, 184399, 206793
New mail UI on Walla requires IE-style event capture
Walla workaround for white-space issue

walmart.com

Walmart hides "find in store" popup unintentionally
Fix navigation bar on walmart.com

wap.flycell.com.br

Avoid CSS input validation of hidden inputs

wap.smartone-vodafone.com

Re-initialize page on back to make plugins work correctly

wapp.verizon.net

Verizon mobile webmail service should default to mobile view

weather.com

fix disappearing menu on weather.com
Fix mouse event order of sign in link

westjet.com

Westjet browser sniffing causes reload loop

wetter.rtl.de

Font size adjustments to avoid overlapping on wetter.rtl.de

wikimapia.org

Faking oncontextmenu support on wikimapia

win.mail.ru

Mail.ru: Allow addition from address book

worldofwarcraft.com

Mouseover popups do not appear due to document.all sniffing

www.etrade.wallst.com

Working around E*Trade site's security policy violation (second part)

www.google.com

On narrow screens Google's navigation bar can wrap and cause overlap

www.ojogo.pt

Fix iframe width on ojogo.pt

www.price-drop.tv

price-drop.tv: enable login button

yam.de

iframe layout fix for yam.de

yellowpages.com.au

Yellow pages event capture fix

youtube.com

Fix bad painting of dropdown menus

zdnet.com.com

ZDnet video site plays non-existing files if browser is Opera

zoover

fix disappearing menu on zoover sites

aumypage.duogate.jp

au my page XMLHttp re-use issue

live.vodafone.com

Display Vodafone's Google search site in Normal Zoom by default

m.espn.go.com

Content goes over screen width on m.espn.go.com

mobile.nytimes.com

Logo image goes over screen width on mobile.nytimes.com

mobile.vzwapp.com

VZW mobile start page has colored span elements that overlap images
VZW mobile portal does not trigger mobile view

my.tnt.com

force all images to load before printing TNT delivery sheet

wap.smart.com.ph

WAP site on smart.com.ph serves XHTML content without xmlns
Automatically re-parse XHTML content with parse errors as HTML

weather-mobile.weatherbug.com

Banner goes over screen width on weather-mobile.weatherbug.com

xhtml.emome.net

emome.net wap portal does not trigger mobile view

http://www.dowwallpaper.com/index.htm

redirect to frame content to prevent rendering error for small buffer size

/sample_lr.html

Sun Webmail fails to set document.domain due to browser sniffing

bing.com/maps/

Fake oncontextmenu support

http://www.google.com.tw/

Autocomplete makes typing very slow on google.com.tw

https://www.bookryanair.com/skylights/cgi-bin/skylights.cgi

Selects are reset if an option is changed from onchange.

legolandholidays.dk

Fix to show relative positioned table contents

Maconomy/MaconomyPortal

Fix unload form submit behavior on Maconomy portals

wp-admin

Wordpress Admin prev/next link styling makes them unclickable

Patched scripts

Old versions of the following popular script libraries, all of which fail in Opera:
- "Sothink menus" versions 3.72 and earlier; changes browser detection to make the menus use the correct code in Opera.
- "Milonic menus": changes browser detection to make the menus use the correct code in Opera.
- "HierMenus": changes browser detection so the menu is not disabled in Opera.
- "Likno AllWebMenus", builds earlier than 498; changes browser detection to make the menus use the correct code in Opera.
- "Menu/Pop Menu": (HV Menu); changes browser detection so the menu is not disabled in Opera.
- "Ultimate Dropdown Menu": changes browser detection so the menu is not disabled in Opera.
- "OpenCube menus": changes browser detection to make the menus use the correct code in Opera.
- "Coolmenus": changes browser detection to make the menus use the correct code in Opera.
- "DynAPI": changes browser detection to make the library use the correct code in Opera.
- "Transmenus": changes browser detection and code to make the library use the correct code in Opera.
- "TinyMCE" 2.x versions: works around a bug that prevents enabling editing mode. 3.0.x versions: works around an issue that breaks the enter key
working around incompatibility with prototype - argument extends array but not all methods work correctly
Prototype requires function.toString to return a unique string per function
The required attribute does not take the value false according to WebForms2 - remove "required=false" from form elements
The constructor property of DOM nodes should not be Object
Constructor property of event should be Event interface
Remove non-breaking spaces inserted by rich text editing bug
Fake support for MozOpacity properties on style object
Generic JS library patches
Generic prepareFakeDesignMode
Compatibility layer for Google Gears initialization script
Router configuration SCRIPT in OPTION tag fix
PDF security patch
Generic patch to support window.scrollX, window.scrollY
document.domain can not be set to last TLD
NHK and iui.js relies on array indexOf
Generic fix for hidden password boxes
Asia-region Generic Patches
Support for contentEditable and designMode
Generic patches (Windows mobile)
Make sure plugin sniffers detect the correct Flash API version

Note to webmasters

There are several reasons why Opera might modify your pages. These include:

Opera may prevent a browser detect on your pages from causing problems.
Opera may fix incompatible, invalid, out-of-date, or problematic code used on your pages.

If you think Opera is modifying your page incorrectly or unnecessarily, or if you have removed the cause of the problems, please report it in our bug tracking system.

If you wish to disable Browser JavaScript to allow you to test your fixes, you can do this by setting Browser JavaScript to 0 in Opera6.ini. A quicker way to do this is to access opera:config#Browser JavaScript, since toggling this setting in opera:config does not require restarting Opera.

Opera