A small but silly one: breaking middle and right click functionality for links.

An auction site I use loads in the list of auctions after the rest of the page loads in, and also doesn't let you open links with middle click or right click>new tab, because the anchor elements don't have href attributes. So that site is a double-dose of having to open auctions in the same tab, then going back to the list page and losing my place in the list of auctions due to the late load-in and failure to save my scroll location.