May be you people are already aware of these “web developer” plug-ins.

• Internet Explorer Developer Toolbar
• Web Developer Extension for Mozilla Firefox

Some of the features a developer/designer may interested in are –

• Preview of website in various resolutions
• Show outline on tables, divs, tds, images etc.
• Cache and cookie management
• W3C validations
• Ruler, Color picker
• DOM tree view
• Disable/Enable css, scripts etc.

IE - http://www.microsoft.com/downloads/details.aspx?familyid=e59c3964-672d-4511-bb3e-2d5e1db91038&displaylang=en Mozilla - http://chrispederick.com/work/web-developer/