Question about "CSS Rollover" Tutorial

The tut can be found here:
http://www.kirupa.com/web-tech/css_rollovers.htm written [size=1][color=#666666][size=2][color=black]by Sam Kellett, aka Halikidiki. I’d like to PM him if anyone knows where I can find him.[/color][/size][/color][/size]

My problem is: After going through the tut (which was awesome by-the-way) my hover:image appears to jump when rolling over. I followed the dimensions accordingly. Of course my image is different; the top image is text and the hover: image is the same text with a box around it.

How do I solve the jumping effect in the rollover process?

Thx in advance for any helps I may receive.