Here’s a demo I made displaying a rounding error with IE and my solution to it.
Basically, any time you’ve got two or more floats next to each other and their widths, defined in percentages, equals 100%, you’re going to run into this rounding error.
I’ve seen this a lot, but never really focused on it as I found that other hacks would sometimes resolve the issue.
But the hack presented in the demo ( setting negative margins on the right-most floated block element ) works much better and is less hacky. I like it.
Hopefully you will find it useful.