IE7 shipped with a new and improved Page Zoom feature that lets you zoom more than just the text of the page. While I think I like it (there's many saying it will make developers lives easier), it has its bugs.
The most recent one I've seen is its failure to correctly calculate text width. I've found no fix for this, except adding a right-margin, something that renders the box too wide instead of too narrow. The calculation seems to a little bit better with
font-style: italic;, but it's still incorrect.
It you have a fix, let me know in the comments (the usual stuff does not seem to work).
I guess the Page Zoom is hard to implement, since basic things like that breaks. At the other hand, Opera has had it for years, and Firefox will in version 3. I really look forward to explaining this to customers :)