Websites look wrong

Gecko-based applications, like the Mozilla Suite and Firefox are designed from the bottom up to support sites written with W3C standards. However, other browsers sometimes use alternate methods to format pages which are not supported by the Mozilla Suite or Firefox. The best long term solution is to respectfully ask the website developer if they can make their page work in Mozilla. For help on doing this, visit the Tech Evangelism project page. If this is not possible, there are a few things you can try to get the site to work as designed.

Possible solutions for website developers

• Make sure the coding of your website is valid and up to standards (e.g., supports multiple OSes and browsers). For help on this please visit W3C.org (World Wide Web Consortium) and HTMLhelp.com.
• To check the validation of your website visit both HTML Validator and CSS Validator.
• View and edit website coding in Firefox through a real-time HTML editor [1].
• Firefox extensions HTML Validator and Web Developer can be helpful with validation and HTML source.
• There are also multiple tools that can validate your website for you, e.g. HTML Tidy, HTML-Kit, and W3C tools.

Possible solutions for users

• Make sure "Tools -> Options -> Web features -> Load Images [For originating web site only]" is unchecked. Reload page if needed.
• Clear everything out such as your cache, and cookies: "Tools -> Options -> Privacy" then exit Firefox and try it again.
• Go to "View -> Page style" and change "No Style" to whatever is there if it's not already checked.
• If you have Adblock check it from the status bar to see if anything is being blocked, and remove it from Adblock's preference window: "Tools -> Extensions", then double-click "Adblock".
• "Tools -> Options -> Web features -> Load Images -> [Exceptions]", and remove any culprits and press "OK".
• Make sure your firewall isn't blocking the Mozilla Suite or Firefox from getting page content.
• The page may require cookies or popup windows. Enable these features via "Tools -> Options -> Web Features" in Firefox (see also [2]).
• The page may require JavaScript. Configure JavaScript via "Tools -> Options -> Web Features (-> Advanced)" in Firefox.
• The page may require Java. Enable Java via "Tools -> Options -> Web Features" in Firefox. Alternatively, try installing Sun's Java (J2SE JRE). Detailed help for Firefox (but this can also be used for the Mozilla Suite).
• If the problem is with a plugin, like Flash or Windows Media Player, look at this forum thread.
• See Error loading some websites.
• Sometimes layout problems can be fixed by forcing a page reflow.
• Install a user agent spoofer, such as User Agent Switcher extension, to make the web site think you are using a different browser.
• Sites that almost work, but need modification, can sometimes be fixed with GreaseMonkey and an onslaught of other extensions, which would allow you to change how the page looks and acts. You can try to change the page yourself, or see if someone else has written a fix (for GreaseMonkey, a script aka GMS or GM Script).
• If everything else fails, on Windows, you can install IE View which allows you to right-click open pages in IE.
• If nothing worked for you this far (and Internet Explorer is not your weapon of choice) then the website's coding might be flawed and not up to standards (with poorly written coding). As a last resort try contacting the webmaster and complain about the nonfunctional website.

Gecko limitations

• Cannot use Microsoft's Java VM. Use an alternative, such as Sun's Java VM.
• Cannot render VML or do VML scripting. Try using SVG instead (note that official builds don't currently include SVG support).
• Menus and other scripts that use document.layers will not work. Developers: see this site for more information.
• Partial support for document.all and document.<id> (but not document.<name>) has been added to Firefox 1.0.
• Occasionally page layouts will be displayed incorrectly due to incremental reflow bugs in the current release of Firefox. Oftentimes a more recent build will render the same pages correctly.
• ActiveX controls are not supported in most Gecko browsers. If possible, use a plugin interface instead, which is possible with Windows Media Player.
• Microsoft Windows Update must, by design, be run in Windows on Internet Explorer. There are some 3rd party sites that allow access to some updates, such as WindizUpdate.
• Firefox strictly interprets the W3C spec for HTML comments; as a result, some of the contents of malformed comments might be rendered. See bug 102127.