function resize() {
	var scnWid,scnHei;
	if (self.innerHeight) // all except Explorer
	{
		scnWid = self.innerWidth;
		scnHei = self.innerHeight;
	}
	else if (document.documentElement && document.documentElement.clientHeight)
		// Explorer 6 Strict Mode
	{
		scnWid = document.documentElement.clientWidth;
		scnHei = document.documentElement.clientHeight;
	}
	else if (document.body) // other Explorers
	{
		scnWid = document.body.clientWidth;
		scnHei = document.body.clientHeight;
	}
	var topheight=document.getElementById("topDiv").offsetHeight;
	var botheight=document.getElementById("bottomDiv").offsetHeight;

	var newCenterHeight = scnHei-topheight-botheight-2+"px";
	
	document.getElementById("centerDiv").style.height=newCenterHeight;
}

resize();