Internet Explorer on Windows completely ignores closing </li> tags. This has two annoying effects.
1. The first is that if the list item contains a block level link, any blank space after the LI is rendered as a blank line (workaround is to remove the blank space, or set the display:inline; style on the LI elements):
2. If another UL is nested inside the UL, but NOT inside a LI (NOTE - this is invalid HTML, the nested UL should be a child of an LI element), IE inserts the UL inside the preceding LI - this alters both the response to CSS, and the DOM of the document:
Microsoft are well aware of this problem, and have ignored it since IE4.