On Windows XP:

Delete the files under
C:\Documents and Settings\%Username\Local Settings\Application Data\Microsoft\Windows Live Contacts
but NOT the %Username@[msn]/[hotmail]/[live].com files.

On Windows Vista

Delete the files under
C:\%username%\Local Settings\Application Data\Microsoft\Windows Live Contacts
but NOT the %Username@[msn]/[hotmail]/[live].com files.

Thanks go to http://philipyeoh.com/blog/ for the post!

(source http://speckyboy.com/2008/11/02/27-indispensable-web-design-and-development-firefox-extensions/)

Though all of these extensions are useful, I found that I would mostly rely on the following:

1. Web Developer (a web developer’s RIGHT hand)
   
   
2. Firebug
   
   
   (debug/analyze/edit page’s HTML, CSS, Javascript, AJAX calls, CDN connections among other tools)
   
3. YSlow!
   
   
   (Yahoo tool for analyzing page loading speed showing elements’ sizes and network connections the page is making)
   
4. CSS Viewer
   
   
   (visually analyze the page’s CSS)
   
5. Extended Status Bar (does a similar job to that of YSlow!)
   
   
   (useful to analyze the time a page will take to load including images)
   
6. NoScript (allow/block iframes, Flash, Java Applets, Javascript, cross-domain scripts. A useful for slow loading pages and a tool to protect one’s privacy!)
   
   
7. EditCSS
   
   
   (modify the current CSS – helpful in analyzing the cascading rules and specificity)
   
8. Dummy Lipsum
   
   
   (this should be useful for prototyping)
   
9. CSS Validator
   
    
   
10. Image Zoom
    
    
    
11. ColorZilla
    
    
    (color picker for web pages)
    
12. Abduction!
    
    
    (takes screenshot of the page/selection including the scrollable/hidden area and that is 4 FREE!)
    

(thanks to SpeckyBoy.com)