<p>Can anyone suggest some good browser add-on tools/extensions to help with development?
I have firebug installed in Firefox which is great for dealing with CSS, HTML and javascript; any other suggestions?</p>

<p><a href="https://addons.mozilla.org/en-US/firefox/addon/1843" rel="nofollow noreferrer">Firebug</a></p>

[{'answer_id': 17567, 'author': 'John Topley', 'author_id': 1450, 'author_profile': 'https://Stackoverflow.com/users/1450', 'pm_score': 2, 'selected': False, 'text': '<p>The other must-have for Firefox is Chris Pederick\'s <a href="http://chrispederick.com/work/web-developer/" rel="nofollow noreferrer">Web Developer Toolbar</a>.</p>\n'}, {'answer_id': 17569, 'author': 'Ishmaeel', 'author_id': 227, 'author_profile': 'https://Stackoverflow.com/users/227', 'pm_score': 1, 'selected': False, 'text': '<p><strong>Developer Console</strong> and <strong>DOM Snapshot</strong> for Opera:</p>\n\n<p><a href="http://dev.opera.com/tools/" rel="nofollow noreferrer">http://dev.opera.com/tools/</a></p>\n\n<p>Awesomeness is that these are bookmarklets implemented with JS. Suckiness is that they require the Internetz.</p>\n'}, {'answer_id': 17588, 'author': 'Xetius', 'author_id': 274, 'author_profile': 'https://Stackoverflow.com/users/274', 'pm_score': 3, 'selected': False, 'text': '<p>For Firefox:</p>\n\n<p><a href="http://getfirebug.com/" rel="noreferrer">Firebug</a> is awesome for investigation and development.</p>\n\n<p><a href="http://chrispederick.com/work/web-developer/" rel="noreferrer">Web Developer Toolbar</a> is good also.  Really helps with CSS and page layout stuff as well as much more.</p>\n\n<p>I also use <a href="https://addons.mozilla.org/en-US/firefox/addon/3829" rel="noreferrer">Live HTTP Headers</a> (I think it is called, but it is on my work machine, so can\'t find the link now).  Which has helped us out with caching issues and the like.</p>\n\n<p>I do a lot of mobile phone development, so I also use <a href="http://chrispederick.com/work/user-agent-switcher/" rel="noreferrer">UserAgent Switcher</a>.  Very helpful for pretending to be different mobile phones.</p>\n\n<p>I tend to only use Firefox for development, and just test in other browsers as most do not have the extensive range of plugins to aid development that Firefox does.</p>\n'}, {'answer_id': 17602, 'author': 'Vaibhav', 'author_id': 380, 'author_profile': 'https://Stackoverflow.com/users/380', 'pm_score': 2, 'selected': False, 'text': '<p>You should definitely install Safari. It has a number of tools built-in. I use it in combination with other browsers all the time.</p>\n\n<ul>\n<li>Network Timeline</li>\n<li>Error Console</li>\n<li>Web Inspector</li>\n<li>Snippet Editor</li>\n</ul>\n\n<p>Plus it lets you set the user agent for your requests. </p>\n\n<p>Consider this, it has a separate top-level menu called <strong>Develop</strong>.</p>\n'}, {'answer_id': 17616, 'author': 'Cebjyre', 'author_id': 1612, 'author_profile': 'https://Stackoverflow.com/users/1612', 'pm_score': 4, 'selected': True, 'text': '<p>Firefox:</p>\n\n<ul>\n<li><a href="https://addons.mozilla.org/en-US/firefox/addon/1913" rel="nofollow noreferrer">Inspect This</a> if you use the DOM Inspector at all</li>\n<li><a href="https://addons.mozilla.org/en-US/firefox/addon/539" rel="nofollow noreferrer">Measure It</a> for telling you pixel distances (if you need that)</li>\n<li><a href="https://addons.mozilla.org/en-US/firefox/addon/35" rel="nofollow noreferrer">IE View</a> or <a href="https://addons.mozilla.org/en-US/firefox/addon/4641" rel="nofollow noreferrer">Safari View</a> for ease of testing in other browsers</li>\n<li><a href="https://addons.mozilla.org/en-US/firefox/addon/249" rel="nofollow noreferrer">HTML Validator</a> if you care about validation</li>\n<li><a href="https://addons.mozilla.org/en-US/firefox/addon/1815" rel="nofollow noreferrer">Console<sup>2</sup></a> to improve your js error console</li>\n<li>The <a href="https://www.squarefree.com/bookmarklets/webdevel.html" rel="nofollow noreferrer">Javascript Shell</a> bookmarklet is also handy (and look at the others there as well)</li>\n</ul>\n\n<p>Edit: This is in addition to the <a href="https://addons.mozilla.org/en-US/firefox/addon/60" rel="nofollow noreferrer">Web Development Toolbar</a> mentioned by others</p>\n'}, {'answer_id': 17621, 'author': 'Aquatic', 'author_id': 2080, 'author_profile': 'https://Stackoverflow.com/users/2080', 'pm_score': 2, 'selected': False, 'text': '<p>In case of IE, next tools can be useful</p>\n\n<ul>\n<li><a href="http://www.microsoft.com/downloads/details.aspx?FamilyId=E59C3964-672D-4511-BB3E-2D5E1DB91038&amp;displaylang=en" rel="nofollow noreferrer">Microsoft Developer Toolbar</a> - dom|styles viewer</li>\n<li><a href="http://www.fiddlertool.com/fiddler/" rel="nofollow noreferrer">Fiddler HTTP Debugger</a> - http monitor</li>\n<li><a href="http://www.blazingtools.com/is.html" rel="nofollow noreferrer">Instant source</a> - dom|styles viewer</li>\n<li><a href="http://www.my-debugbar.com/wiki/CompanionJS/HomePage" rel="nofollow noreferrer">Companion.JS</a> - dom|styles viewer, extended error console</li>\n</ul>\n\n<p>The "uber" extension for IE - "Developer Tools", provided as a part of IE8</p>\n'}, {'answer_id': 17658, 'author': 'Mo.', 'author_id': 1870, 'author_profile': 'https://Stackoverflow.com/users/1870', 'pm_score': 1, 'selected': False, 'text': '<blockquote>\n<p>Firefox:</p>\n<p>Inspect This if you use the DOM Inspector at all</p>\n<p>Measure It for telling you pixel distances (if you need that)</p>\n<p>IE View or Safari View for ease of testing in other browsers</p>\n<p>HTML Validator if you care about validation</p>\n<p>Console2 to improve your js error console</p>\n<p>The Javascript Shell bookmarklet is also handy (and look at the others there as well)</p>\n<p>This is in addition to the Web Development Toolbar mentioned by others</p>\n</blockquote>\n<p>This list by Cebjyre is nearly complete (since FireBug was already mentioned in the question). I would only add <a href="http://tamperdata.mozdev.org/" rel="nofollow noreferrer" title="Tamperdata">Tamperdata</a>. From time to time it is very useful.</p>\n'}, {'answer_id': 17682, 'author': 'Shadow2531', 'author_id': 1697, 'author_profile': 'https://Stackoverflow.com/users/1697', 'pm_score': 2, 'selected': False, 'text': '<p>Opera has:</p>\n\n<p>Dragonfly (tools -> advanced -> developer tools)</p>\n\n<p><a href="http://my.opera.com/dragonfly/blog/2008/06/09/the-debug-menu-and-the-new-weekly" rel="nofollow noreferrer">Debug Menu</a></p>\n\n<p><a href="http://www.opera.com/support/tutorials/userjs/specs/" rel="nofollow noreferrer">UserJS methods for intercepting things</a></p>\n\n<p>opera:config#CompatMode%20Override for forcing quirks or standards mode</p>\n\n<p><a href="http://widgets.opera.com/category/web-developer/" rel="nofollow noreferrer">Web developer widgets</a></p>\n\n<p>You can view source of files, edit them, apply changes and reload from cache.</p>\n'}, {'answer_id': 17757, 'author': 'grapefrukt', 'author_id': 914, 'author_profile': 'https://Stackoverflow.com/users/914', 'pm_score': 0, 'selected': False, 'text': '<p>Other than the excellent tools already mentioned, I find <a href="http://www.charlesproxy.com/" rel="nofollow noreferrer">Charles</a> to be extremely useful. Especially since I do alot of work with Flash Remoting which it handles excellently.</p>\n<blockquote>\n<p>Charles is an HTTP proxy / HTTP monitor / Reverse Proxy that enables a developer to view all of the HTTP traffic between their machine and the Internet. This includes requests, responses and the HTTP headers (which contain the cookies and caching information).</p>\n<p>Charles can act as a man-in-the-middle for HTTP/SSL communication, enabling you to debug the content of your HTTPS sessions.</p>\n</blockquote>\n<p>It\'s crossplatform, costs $50, but there\'s a &quot;30 minute per session&quot;-evaluation you can download.</p>\n'}, {'answer_id': 25171, 'author': 'travis', 'author_id': 1414, 'author_profile': 'https://Stackoverflow.com/users/1414', 'pm_score': 0, 'selected': False, 'text': '<p>Here\'s what I use:</p>\n\n<p>Firefox:</p>\n\n<ul>\n<li><a href="http://www.mozilla.org/projects/inspector/" rel="nofollow noreferrer">DOM Inspector</a>: I use this more than anything else for web development</li>\n<li><a href="http://gemal.dk/mozilla/launchy.html?project=launchy" rel="nofollow noreferrer">Launchy</a>: for opening sites in other browsers/apps</li>\n<li><a href="http://tamperdata.mozdev.org/" rel="nofollow noreferrer">Tamper Data</a>: this can be helpful for debugging GET/POST requests</li>\n<li><a href="http://chrispederick.com/work/web-developer/" rel="nofollow noreferrer">Web Developer Toolbar</a>: this has so many handy features for debugging: the W3C validation tools, built-in ruler, resizing tools, source manipulation, easy cache/css/script tools</li>\n</ul>\n\n<p>IE:</p>\n\n<ul>\n<li><a href="http://www.microsoft.com/downloads/details.aspx?FamilyId=E59C3964-672D-4511-BB3E-2D5E1DB91038&amp;displaylang=en" rel="nofollow noreferrer">Internet Explorer Developer Toolbar</a>: nowhere near as handy as the Firefox one, but at least it gives you a decent DOM Inspector</li>\n</ul>\n\n<p>Misc:</p>\n\n<ul>\n<li><a href="https://www.squarefree.com/bookmarklets/webdevel.html" rel="nofollow noreferrer">Jesse\'s handy bookmarklets</a>: the <a href="https://www.squarefree.com/bookmarklets/webdevel.html#shell" rel="nofollow noreferrer">shell</a> bookmarklet is especially handy</li>\n<li>I also install <a href="http://www.apple.com/safari/" rel="nofollow noreferrer">Safari</a> and <a href="http://www.opera.com/" rel="nofollow noreferrer">Opera</a>, but mostly just use them for testing and benchmarking since their dev tools aren\'t as robust as Firefox, and they aren\'t as buggy as IE.</li>\n<li><a href="http://en.wikipedia.org/wiki/Lynx_%28web_browser%29" rel="nofollow noreferrer">Lynx</a>: I use this to make sure that any JS-heavy sites still work so that I\'m sure they\'ll look OK to google, screen readers, and any other bot-like app.</li>\n</ul>\n'}, {'answer_id': 26883, 'author': 'dlamblin', 'author_id': 459, 'author_profile': 'https://Stackoverflow.com/users/459', 'pm_score': 1, 'selected': False, 'text': '<p>Here\'s my development oriented add-ons for <a href="http://www.mozilla.com/en-US/firefox/" rel="nofollow noreferrer">Firefox 3</a>:</p>\n\n<ol>\n<li><a href="http://chrispederick.com/work/web-developer/" rel="nofollow noreferrer">Web Developer</a></li>\n<li><a href="http://getfirebug.com/" rel="nofollow noreferrer">Firebug</a>\n\n<ol>\n<li><a href="http://www.janodvarko.cz/firecookie" rel="nofollow noreferrer">Firecookie</a></li>\n<li><a href="http://www.firephp.org/" rel="nofollow noreferrer">FirePHP</a> </li>\n<li><a href="http://xrefresh.com/rainbow" rel="nofollow noreferrer">Rainbow</a></li>\n</ol></li>\n<li><a href="http://tamperdata.mozdev.org" rel="nofollow noreferrer">TamperData</a></li>\n<li><a href="http://code.google.com/p/poster-extension/" rel="nofollow noreferrer">Poster</a></li>\n<li><a href="http://fireftp.mozdev.org/" rel="nofollow noreferrer">FireFTP</a> </li>\n<li><a href="http://reloadevery.mozdev.org/" rel="nofollow noreferrer">ReloadEvery</a></li>\n<li><a href="http://selenium-ide.openqa.org/" rel="nofollow noreferrer">Selenium IDE</a></li>\n</ol>\n'}, {'answer_id': 260173, 'author': 'ojrac', 'author_id': 20760, 'author_profile': 'https://Stackoverflow.com/users/20760', 'pm_score': 1, 'selected': False, 'text': '<p><a href="http://developer.yahoo.com/yslow/" rel="nofollow noreferrer">YSlow</a> is a sweet Firebug addon for troubleshooting a page\'s load time.</p>\n'}]
['https://Stackoverflow.com/questions/17561', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1762/']