Filtering competitor's ads

The 728x90 leader board format and a couple of other formats do not display the URL on the ad.
I see a competitor's ad showing. How to find out what URL to block?

The only way I can think of, is to temporarily change the format to one that DOES show the URL, then block them. And then change back to 728x90 format.

Am I missing a quicker way? Any help appreciated.

 

You can right-click on the ad and select "view source" to see which URL is being linked. Right-clicking will not count as clicking your own ad.

 

Thanks jamcon.
Rep added.

 

In IE you can se at onMouseOver in Status Bar the url without clicking.

 

Perfect! Rep given

 

you can download adsense preview tool ,i use it.
you can find it on google adsense site.
Search a little.