There are a few tricks you can use there. I guess you just want to show some text over the top of the button graphic. Troubles start when the length of text outgrows the button. Ideally you'd stop that happening. If not you can do things like split the button in two and have markup like this:
Then put the first part of the button background in the A tag using CSS and the other part to the right of the SPAN's background using CSS.