Useful Firefox Add-ons for Bloggers/Website Owners

Firefox, in my opinion, is the best browser out there. If you are a blogger or a website owner, you may find the following add-ons useful. (Some may even be useful to you if you are just a regular user)

• NoDoFollow: NoDoFollow is an add-on that highlights all links on a web page that are DoFollow links. This can be toggled off and on via the right click menu. This is useful for checking your links or for looking for DoFollow links on other websites. (Thanks to Ceri Shaw for recommending this one)
  
• Clipmarks: Clipmarks is a Firefox add-on that lets you "Clip" up pages instead of copying and pasting. It preserves formatting (in most cases) and allows you to post directly to many blogging platforms.
• Copy as HTML Link: This handy little add-on allows you to select text and create an HTML Link containing the selected text to the page you have selected it from. It is then stored in the clipboard.
• HTML Validator: Checks the validity of the HTML code on a selected page. Pretty simple and especially useful if you are going for valid HTML. However, this does not work in Linux
  
• IE Tab: This nifty little add-on allows you to view your page in an IE tab while still being inside Firefox. Great for checking how your page looks in IE without having to actually use that garbage browser!
• MeasureIt: This tool allows you to use a ruler to measure out elements and other parts of web pages. It comes in really useful when trying to clean your HTML code.
• Web Developer: This is by far the most useful addon when messing around with your Web Pages. This add-on creates a toolbar that allows you to change parts of your page, view source code, resize things, validate code, and much more.
• Adblock Plus: This is a great tool to stop those annoying advertisements that get in your way of viewing content. You can even use wildcards so similar ads will not be loaded again. (Please note that I do not condone blocking banner advertisements or other ads that are not making it hard for you to view content. Many websites are supported by these advertisements and they deserve the ad revenue.)
  

If you happen to have any more add-ons that should be added to this list, please comment with a link to it. You will be credited for the contribution.