How to mark all unread email as read in GMAIL

Hello All, Recently I came across this wonderful video which I am sharing with you guys, Cheers !

There are few other ways to do it too, I have listed them below
1. http://www.apejet.org/aaron/blog/2008/06/08/gmail-tip-mark-all-unread-mail-as-read/

2. http://lifehacker.com/396928/mark-all-unread-messages-as-read-in-gmail