Well no - they won't. You aren't calling them at all - you are just adding them to the list of methods to call when you do action the delegate. In fact, each time you press the button, you add four more methods to the list, so if you did call the delegate itself, after the first press it would call each one once, after the second press it would call each one twice, and so on.
Try this:
protected void Page_Load(object sender, EventArgs e)
{
myevent += new mydelegate(method1);
myevent += new mydelegate(method2);
myevent += new mydelegate(method3);
myevent += new mydelegate(method4);
}
protected void Button1_Click(object sender, EventArgs e)
{
if (myevent != null)
{
myevent();
}
}