Why is the window.close() works in IE browser but not FireFox?

Hello,

 I used the ClientScriptManager for the window close in the code behind and it did closeout the window when I click the "Cancel" button in IE browser but not in the FireFox browser, so I'm wondering why is it, can anyone helps me with this?  Thanks

Here is the code for the window close and it is place in the cancel control event
ClientScriptManager csm = Page.ClientScript;
csm.RegisterClientScriptBlock(this.GetType(), "", "<script>parent.window.close();</script>"); Go to the complete details ...