Google will be updating its URL policy for every AdWords account. Beginning on April 1, 2008, your display URL must match your landing URL.
For some people this may come as news, meaning that they did not know that the URL's did not have to match with the landing URL to begin with.
Below is an example of an AdWords ad that does not share the same display and landing URL. The ad's display URL shows www.IPOWERWEB.com/products/ - but the display URL should really be http://www.Blog.IPOWERWEB.com because the IPOWERWEB Blog will be the landing URL.
So as of April 1, 2008 the display URL for the ad above will have to be http://www.Blog.IPOWERWEB.com. Here is an example of what the ad will now look like.