#34: assume that all visitors will want to view their site fullscreen, and do so by resizing the page to the height and width of the screen and then moving to the top-left corner. Because obviously no-one will have their browser at anything smaller than the size of the screen, and obviously no-one will ever want to have two windows visible at once. Not to mention that obviously no-one runs a multi-monitor setup either.
#35: create a website that has a fixed-width layout. Because obviously everyone uses 800x600. Especially annoying when combined with #34.