Have you heard of Internet Explorer Developer Toolbar? This is an add-in for IE 6.0 and above that allows you to track, enable and disable different elements and features of the current loaded page in IE. For example you can disable all CSS for the page and see how it looks like without it. Or you can outline all table and table cell and show image dimensions or hide all the images. This tool is amazing. I only reason that I did not use it before is because it is still Beta 3 and you know how much I hate browser add-ins.
Still it seems quite stable for now, so I am going to keep it, if it continues to be dutiful add-in.
Here is list of features:

• Explore and modify the document object model (DOM) of a Web page.
• Locate and select specific elements on a Web page through a variety of techniques.
• Selectively disable Internet Explorer settings.
• View HTML object class names, ID’s, and details such as link paths, tab index values, and access keys.
• Outline tables, table cells, images, or selected tags.
• Validate HTML, CSS, WAI, and RSS Web feed links.
• Display image dimensions, file sizes, path information, and alternate (ALT) text.
• Immediately resize the browser window to a new resolution.
• Selectively clear the browser cache and saved cookies. Choose from all objects or those associated with a given domain.
• Choose direct links to W3C specification references, the Internet Explorer team weblog (blog), and other resources.
• Display a fully featured design ruler to help accurately align and measure objects on your pages.
• Find the style rules used to set specific style values on an element.
• View the formatted and syntax colored source of HTML and CSS.

The Developer Toolbar can be pinned to the Internet Explorer browser window or floated separately.

This Beta 3 version of the toolbar contains functionality and stability enhancements over previous versions, including:
• Style Tracer: Right mouse click on a style value for an element and select Style Tracer to find the style rule that is effecting that value.
• CSS Selector Matches: View a report of all style rules set and how many times they are used on the current page.
• View Source: View the formatted and syntax colored source of the original page, currently rendered page, element or element with the styles that are effecting it.
Your feedback is greatly appreciated. Please visit the Developer Toolbar Wiki on Channel 9 to enter bug reports, comments, and suggestions.

Supported Operating Systems: Windows 2000; Windows Server 2003; Windows Vista; Windows XP
Internet Explorer Developer Toolbar requires Internet Explorer 6.0 or later.