Is it a Tab or a Button?

A pet peeve of mine is when a web site uses both tabs and buttons that look the same. This is especially bad when the buttons appear right below the tabs.

When you are quickly looking at this GUI it is easy to think the buttons are tabs and you have to take a few moments to find standard functions, like Delete.

Here is an example I recently saw on an otherwise OK Web Mail GUI. I have marked it up so yoy can tell the difference, but imagine you where looking at this quickly without the mark up.

So what would help?

Make the buttons look more like a real physical button with a different style.