From Microsoft, currently in beta, is the Internet Explorer Developer Toolbar.

Several outstanding features: an on screen ruler (you can see it in the screen shot above) with some useful switches:

Also included is the DOM Explorer (more below about that), find an element by clicking feature, validation, cache and cooking clearing and much more!

In the first screen shot, I have the toolbar configured to show DIV element outlines along with the CLASS and ID information for each element.

There’s a very slick DOM Explorer toolbar also available:

You can walk the DOM tree and explore the structure of the document and the styles that are applied to any given element. VERY handy. The toolbar also will “unpin” if you don’t want it attached to the browser window.

I’m not going to list all of the features here … that’s on the download page.

I’ve used the one built into Firefox and been happy with that … this seems to be at least a clone, if not better!

My hats off to the Microsoft developers for this great new IE toolbar.

Warning: According to reports, this will not currently work in Windows Vista as of Sept 2005.