function screen_size(){		
	  var myWidth = 0, myHeight = 0; myMaindivHeight = 0; myMaindivWidth = 0; myTopMargin = 0; myLeftMargin = 0;
	  if( typeof( window.innerWidth ) == 'number' ) {
		//Non-IE
		myWidth = window.innerWidth;
		myHeight = window.innerHeight;
	  } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
		//IE 6+ in 'standards compliant mode'
		myWidth = document.documentElement.clientWidth;
		myHeight = document.documentElement.clientHeight;
	  } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
		//IE 4 compatible
		myWidth = document.body.clientWidth;
		myHeight = document.body.clientHeight;
	  }
	  myMaindivHeight=document.getElementById('maindiv').offsetHeight;
	  myMaindivWidth=document.getElementById('maindiv').offsetWidth;
	  myTopMargin=Math.max((myHeight-myMaindivHeight)/2-3,3);
	  
	  //window.alert("TopMargin=(" + myHeight + " - " + myMaindivHeight + ")/2 = " + myTopMargin + "px");
	  //myLeftMargin=Math.max((myWidth-myMaindivWidth)/2,0);
	  //document.getElementById('maindiv').style.margin = myTopMargin+"px 0 0 " + myLeftMargin +"px";
	  
	  document.getElementById('maindiv').style.margin = myTopMargin+"px auto";
	}