My personal list of website peeves:
 - Click here to enter -- Duh!? I already entered the url, doesn't that mean I want to enter?
 - anything that says UNDER CONSTRUCTION -- no informational value. Everything on the internet is under construction
 - more than 2 frames in a page - on rare occasion, I can stomach two frames.
 - using javascript and layers for something that could be done with standard html - don't use javascript to display text, for example
 - websites that play music - saw a sig on /. that said "If I wanted your site to make music, I'd have turned on the radio"
 - websites that have all info in non-html or text formats like doc, xls, pdf, ps - Thanks for nothing - just post the info and use html or text. More info and file formats are nice, but put the info in text first.
 - websites that try to determine your browser type and give you messages about needing a different browser - deal with what I have. You're in no position to require me to do anything.
 - popup ads - did I ask you to open a window?
 - any site that says: "Welcome to my website" - duh!
 - more than one animated gif on a page
 - pages that maximise - you know I MINIMIZED you for a reason...