Can I Set My Mac To Bypass The Login Screen In OS X Lion?
Boot up your Mac from an administrator account (this is the default if you only have one account) and go to the Apple menu to System Preferences. Select the Users & Groups panel and then click the lock at the bottom left of the window to unlock it. You will be asked for your password.
Next, click on Login Options and look for a pull down menu called Automatic login. Click on it to select the account that you would like to automatically login to during startup.