How do I center align adsense ads?

Hi,

I have a site coded in xhtml/css, where I use the 468x60 adsense baer.

Immediately below the adsense baer is a h2 heading

I would like the adsense ad to center align. I used

But with this, the h2 heading wraps around the adsense baer.

How do I fix this problem?

Any suggestions would be greatly appreciated.

Thank you,
Ellora.