Dumb Dumb Dumb
Take a close look at this page for BT Global Services (nee BT Ignite, nee BT BuyNet).
Do you see those drop downs on the right hand side?
They're not drop downs. Some bright spark web developer has implemented a dHTML menu to recreate the functionality of a drop down select menu.
I could have probably forgiven that (although don't get me started on a rant about re-implementing perfectly fine UI elements) if it had degraded gracefully, but then to make things even worse, they've made it look like a drop down.
Drop down menus activate upon a click (whether that be from a mouse or a keyboard), expanding to reveal the available options. Once they lose focus they collapse again.
Not these bastardised dHTML versions.
They expand merely by hovering over them, thereby breaking the users expectations of how a widget that looks like a drop down should behave and just generally getting in the way when you're trying to read the content.
Keep user surprise to a minumum, fulfil their expectations of interface behaviour. They'll thank you for it.