How do i have an auto number in browser tab?

I am currently building a web email client and i was wondering how to code a function into it that shows a number appear telling you that you have unread mail if you are viewing another tab. Heres an example of what i mean if you don't understand.



That is an example of what i mean from hotmail. If i'm in another tab and an email comes through it comes up with a 1.

How do i go about coding this into mine? Any help would be much appreciated.

 

With the use of Ajax, you can periodically load a page which displays how many unread emails you have recieved. When this is not zero, you can change the title tag.

Example using jquery:

$.POST("ajax/check.php","",function(data){
     if(data==0)document.title="Title";
     else document.title = "Title ("+data")";
}); 

Code (markup):