How will I know that my site will be approved for Adsense program? Make sure that you site does not:

Contain ads for alcohol, beer, liquor or tobacco,

Adult content, pornography...

Weapons promotion...

Illegal content...

Contain hate or racist attitudes,

Promote drugs, prescription drugs, gambling...

A good guideline to go by might be if a site is family oriented.

Check the Adsense Program Policies for more information.