Mail keeps asking for password?

This has been frustrating me for a while now, my iMail constantly asks me to re-input my password and I can't figure out why? It's definitely not my connection, and accessing my mail via the internet has been working fine. Any suggestions?

Check your preferences regarding how often you are having Mail check for new mail. If it is set for too frequent checking, this can happen. Set it for no more often than 5 to 10 minutes and see if that helps.