var bdH = 0;
var hdH = 0;
var ftH = 0;
var winH = 0;
var effWinH = 0;

function fixColumns(){
	var bd = document.getElementById("bd");
	bdH = bd.offsetHeight;
	var hd = document.getElementById("hd");
	hdH = hd.offsetHeight;
	var ft = document.getElementById("ft");
	ftH = ft.offsetHeight;
	var nav = document.getElementById("nav");
	if (navigator.appName=="Netscape") {
		winH = window.innerHeight;
	}
    if (navigator.appName.indexOf("Microsoft")!=-1) {
		winH = document.body.offsetHeight;
     }
	 effWinH = winH - hdH - ftH;
	 if(effWinH > bdH)
		nav.style.height = effWinH + 'px';
	else
		nav.style.height = bdH + 'px';
}