This thing's a freak, I tell ya.
OK, so as I have learned the hard way, be a little industrious when fooling about with the HTML in your profile. I discovered that LC will attempt to re-define, extract, re-code, interperet and otherwise take a hand mixer to your carefully written and oh-so-beautiful code if you edit it right in the box there. You'll end up with style definitions missing, links cut in two, all sorts of madness.
The way to avoid it? Notepad, ladies and gentlemen. Copy that code out of there and save it someplace (which every good web designer does anyway, yes?). Make your edits in notepad, then copy and paste into the profile and hit the button.
Now, skins. This is where you get to do all that wonderful CSS magic (or, as the case may be, tomfoolery). Before you go screwing about with this stuff, especially if you don't know CSS from a hole in the good Earth, do what I've mentioned above: copy it all out, paste it in nodepad and save it. That way if you screw it up you can save yourself.
Perhaps I'll make this a weekly thing, posting little HTML and CSS diddles so people's profiles get in shape. Everyone wants a pretty profile, yes?