Javascript in saparate js file

 if(!Page.IsPostBack)
{
if(!Page.IsClientScriptBlockRegistered("MyScript") )
{
Page.RegisterClientScriptBlock("MyScript","<SCRIPT Language='JavaScript' src='MyJavaScriptFile.js'></SCRIPT>");
}
Button1.Attributes.Add("onclick","PopWindow();");
}


Let's take a lot at a simple .js file:

function PopWindow()
{

alert('hello world from the Javascript file');

}