I'm more and more doing silly things with pseudo elements to add stying to a website design without having to add obtrusive or un-semantic markup.
On a recent project I was using pseudo elements on an hr element to provide some fancy lines for the design.
However when I opened the site in Internet Explorer, surprise surprise there was a problem, the pseudo elements were not visible.
After a bit of digging I discovered that, as I was negatively positioning the pseudo elements I needed to add overflow:visible; to the hr styling.
I'm guessing that in IE anything positioned outside the hr element was not visible but other browsers didn't seem to mind...