You have to have some way to validate the user.  By default, this is using email, but there are plugins that allow you to do manual validation or to automatically validate immediately.

there was a uservalidation plugin i denied it so that user won't have to wait till i validate them, is it necessary to enable it, if yes then any auto mod will work for that :/? and where to validate user.!

google "firefox reloading in a way that will never complete" ;-)