If you're a web developer, you're probably already discovered the beauty of the Firefox browser from the Mozilla foundation. One of the great things about this browser is the concept of browser extensions. like Netscape Plug-ins a decade before them, these enhance the browsing experience. However, where browser plug-ins expanded what you could do with the content in a page, extensions actually change the way the browser works and what the browser can do. There are, in my opinion, the best extensions for web developers.
Ever been annoyed by all those ads and banners on the internet that often take longer to download than everything else on the page? Install Adblock Plus now and get rid of them. - Yeah, this one isn't really related to web development, but it's probably the coolest Firefox extension around, so it deserves mention...
This extension displays the content heirarchy (headers - h1-h6) of the document in a side bar so you can quickly navigate between sections and so you can review this collapsed version of the document to make sure it makes sense.
View the current site's server software, IP address, location flag, and have quick links to Whois and other domain information.
This cool extension validates your HTML as the page is rendered. An icon is displayed in the status bar to let you know of your page is valid, has errors, or has warnings. This is really handy when testing form submit pages or pages behind a firewall or with otherwise restricted access where the validators at Jigsaw can't work. That, and it's great to be able to look into the bottom corner of the window and see whether the page passes or not, without waiting for results to render from W3C. This extension also modifies "view source" so you can see exactly where it thought the problems were, and with notes on what the problem appears to be.
A little friendlier than the 'check links' option in the web developer extension, this checks all links on the page, and then color-codes them so you can see which are valid and which are not...
This sidebar displays page meta-information (metatags, links, etc.) Has automated search engine submission menu. Features include: Watches currently loaded Web page and automatically updates the sidebar. Displays metatags, links, language, base and base folder of the document, MIME type and charset, DTD, root tag, and XML namespace, last modification time, referrer, etc. Keywords are numbered. Warns about duplicate keyword phrases (emphasizes them with red color). Extensible menu for automatic submission to search engines and SEO services.
Screengrab saves entire webpages as images. It will save what you can see in the window, the entire page, just a selection, a particular frame... basically it saves webpages as images.
TAW3 with a click
Check for accessability issues on a page, and quickly deliver a report with explanations of the possible issues so issues can be quickly addressed.
Converts selected unicode text to HTML character codes with right-click.
View Rendered Source Chart
Displays a color-coded source chart for the page, clearly marking nested elements and containers, making even slopy HTML easy to read, and helping to clearly identify nesting errors in HTML source.
This extension provides a number of tools, from quick links to validation services to ability to edit CSS on the fly, from clearing the cache or form variables to outlining block level elements on a page... Dozens of nearly indispensible tools for any web developer.