Don't Click Here!
"Don't Click Here" pages are probably one of the worst creations on the web. Can someone please explain to me why people even waste time making one of those? Not only are they annoying, but they're also stupid and absolutely useless. Obviously, if the page title is something like, "Don't click here," no one is going to click it. I thought the point of having visitor's content was to entertain visitors by having meaningful content, not crap that tells them not to click on a certain link and annoy them with one's stupidity. If you're going to make one of those pages, atleast be original about it (and name it something else..)!

Bad Positioning
I hate when people think that everyone uses/has the same resolution as theirs and decides to code their layouts using center, right, or left positioning (or whatever else it is) to position their iFrame or Div! I guess it's okay when visitors get a warning like "[Resolution] required" or "Looks best on [Resoultion]"

Firefox Incompatible
Believe it or not, a lot of people use Firefox, such as I. Internet Explorer always used to crash on me while I used it, and it always chose the worst times to do so. Because of that, I switched my primary browser to Firefox. I find it annoying when most, if not all, of a person's site is incompatible with my browser (like when everything looks screwed up). I think everyone needs to start making their site so it works on all browsers!