Javascriptery: Tabbed forms
Forms are perhaps the bane of web development for me; you can't get them to look good, you can't find a foolproof way to make them act well and lets not even start of trying to get them into a pacified state, free from the dangers of user input (surprise ending: form input will never be completely trustworthy). A lot of sites would appear to have aesthetically pleasing forms, however this is a careful ruse by them as they sidestep the problem of forms by having only one or two of them, and then they usually only have a few fields. The monstrosities I am required to deal with almost daily are things of grotesque beauty, veritable Rube Goldberg machines of complexity.