I've checked the css-layout in IE11. Seems like it does not perceive the css-rule for the .baseHtml ul li. I've also checked the loaded css.php by the browser and noticed, that the rule would be in there but is not separated from the rule before by a white space. Even though most browsers can handle that, IE seems to struggle with that maybe.
Edit: The format in and around the related section of the css looks weirdly formated anyway, even though this is not a problem in the first place, it is still rather strange.
And that proves my point... friends don't let their friends use IE.
IE has a long history of problems.... not the least of which is it is tied to ONE operating system - whereas the others are able to be used on multiple OS's.