Ask HN: What's your favorite IE quirk?

The one where you had to generate and dynamically size and position an iframe underneath any draggable element that might end up on top of a select. I personally wrote a couple of fixes for that, and there were many more.

My personal favorite is when console was undefined if devtools wasn't opened, making a simple console.log call crash the script.

IE5's interpretation of the CSS box model, where border and padding are included as part of the element width (now available everywhere as box-sizing: border-box). It makes more sense in a lot of cases, but good luck getting your design to look right across browsers without strange incantations like "width: 495px; wi\dth: 500px".