One of the long-standing frustrations for anyone who's tried to edit blog posts or web documents using Mobile Safari is the absence of support for the HTML5 contentEditable attribute. The attribute, which began as an Internet Explorer 5.5 feature and later found its way into most modern browsers, is part of the suite of tools that made it possible for older versions of Google Documents and other inline editors to do their rich-text WYSIWIG editing magic.
Unfortunately, up through iOS 4.3 there's no support for the contentEditable attribute in Mobile Safari, which means that popular web editing tools either don't work at all or have to provide severely limited iOS-specific versions. According to this thread on Hacker News, it looks like things may be changing in iOS 5; preliminary tests on the beta seem to show that the attribute is working as expected in the new version of Safari.
If this does prove out for the final builds of iOS 5 (and that's a reasonably substantial 'if,' since we're still several months away from release), we could be looking at a dramatic improvement in support for virtually all web-based rich text editing tasks on the iPad. For those of us who have struggled with this issue for a while, it's welcome news indeed.
Thanks to Gary Poster for his question.