Open in a new window

Hello,
In my web application i had placed a grid view with image button in the template field of the gridview.
I want to display advertisment using this Imge button.
I had bind the picture to the image button using the command Eval("fieldname") in the edit templates option. an i had set the Postback url also in the same option.

So that when i click on the image. I am reirecting to the url which i given.

But i want to open that advertisment in a new window.


Pleas help me ...