Exclamation Mark with Android Project Name in Eclipse

Solution A

Check errors window.
Try to solve the error there

Solution B

Right click the project, 
select Android and make sure that a build target is checked.
sometimes you need to unchecked it, select a different API, apply settings, and then again select the API that was originally selected.

Solution C

Restart the eclipse

Note :If none of the above solution work then find new one  and tell me  about the new solution in comments .thanks