There were dozens of emails in my gmail inbox that I didn't bother to read. As time went by, they were immersed into the other thousands of emails. It was time to take some actions. Not that I wanted to read them this time, I just didn't want a number shown beside my inbox.
It was weird that gmail.com didn't have a button or link to select all the unread mails. Oh, wait, there was something right above all the listed mails -- "Select: All, None, Read, Unread, Starred, Unstarred". But I clicked the Unread link and nothing happened. That was because all those unread mails were too old to appear on the first page and the Unread link could only select mails on the first page.
To select those mails I wanted, there was an indirect way. Beside the gmail Search the Web button, there was a link in a tiny little font saying Show search options -- What did Google try to hide? LOL.
Clicked that link and a Search Options box showed up. Clicked the Search drop down list and select Unread Mail. Then clicked the Search Mail button and got all my unread mails listed. Then I could select all the Unread mails and mark them as read.