popup from code behind

Hi,
Im trying to code a popup from my code behind which is supposed to pop-up a window which points to a .aspx page I have created. Currently I wrote this but it doesnt seem to be popping anything. I put the link as www.yahoo.com because I wanted to test it.
ClientScript.RegisterStartupScript(this.GetType(), "newWindow", String.Format("<script>window.open('{0}');</script>", "http://www.yahoo.com" , "dialogHeight: 300px;dialogWidth: 600px; center: Yes; help: No; resizable: No; status: No")); Any ideas? Thanks!
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