This came up on Digg when someone was talking about going to any website and make it editable by typing the following into your browser:
javascript:document.body.contentEditable='true'; document.designMode='on'; void 0

Just hit the link and rewrite this page. The effect should work in both IE and Firefox.

What makes this technological miracle possible? Why it's the contentEditable attribute -- not exactly a tag, but one of those oddball features that's sort of in the spec, sort of not. The ability to edit inline content appears to be a microsoft innovation that Mozilla did not want to follow.

In IE, you just bust out "contenteditable" block level attribute to impliment your editor. Try it out by typing your changes into the table itself below.

The Best Walther Matthau Movies (Edit and Change as Needed)

Thanks to utcursch for a 'lil background on all this...

If you want to see a really goofy page editing demo using this feature in IE, go to www.xmlportfolio.com/temp/contentEditable.html. That d00d is even rockin' the execCommand javascript stuff in IE.