When I hover over steam or other tags in the list of my favourite tags, the mouseover popup is shown partially off-screen:

The page fit on-screen before the pop-up, and afterwards a horizontal scrollbar shows up. I can use my arrow keys to move over (and attempt to keep my mouse above the tag), but that's not ideal behavior.

I use Chrome 11.0.696.57 beta; also occurs in IE 8 and Firefox 4.0 and 4.0.1. All on Windows XP.

Edit:

Now it's just the Related Tags, slightly lower on the same sidebar, that exhibit this behavior. (Favorite and Ignored work properly, as Jin describes in his answer.)

Edit 2: Still happening for related tags.