function popWin(fileName, winWidth, winHeight, winName)
{ 

 // Define Window width and height right here so that it can easily be modified. 
 if (!winWidth)
 	var winWidth = 450; 
 
 if (!winHeight)
	 var winHeight = 175; 
	 
 if (!winName) 
 	var winName = "PopUp";
 
 // Midx and Midy will be used to center the window.
 var midx = (screen.width/2) - (winWidth/2); 
 var midy = (screen.height/2) - (winHeight/2)
 
 // Set up the Propeties String
var props = "height=" + winHeight + ",width=" + winWidth + ",screenX=" + midx + ",screenY=" + midy + ",top=" + midy + ",left=" + midx + ",scrollbars=1"; 
  
 window.open(fileName, winName, props);
 
}