how to open email link directly in gmail

Today (well strictly speaking yesterday) morning,when i logged into gmail account, i got a pop-up  asking me to "allow gmail to open all email links".
never heard of this feature;so ignored it.After going through some googling, found this article.

Starting today, thanks to the magic of HTML5 things are getting simpler. Now, when you go to Gmail in Chrome, you will be asked if you want Gmail to open all email links. Say yes, and clicking on email links in any application on your computer will open a fresh Gmail compose window. 

You can set Gmail as your default mail client in Firefox too.

So,nice little trick.Hats off to you google.