var ie4 = document.all;
var ns4 = document.layers;
var ns6 = document.getElementById && !document.all; 

//Center a specified DIV in the browser window
function centerIt (div_id, show, div_height, div_width) {
	var center_height=0;
	var center_width=0;
	
	//For non IE browsers
	if (ns6 || ns4) {
  		center_width = (window.innerWidth/2)-(div_width/2);
  		center_height = (window.innerHeight/2)-(div_height/2);
	}
	else {
		center_width=(document.documentElement.clientWidth/2)-(div_width/2);
  		center_height=(document.documentElement.clientHeight/2)-(div_height/2);
 	}

	if (center_width<0) {
		center_width=0;
	}
	if (center_height<0) {
		center_height=0;
	}
	document.getElementById(div_id).style.left=center_width+"px";
	document.getElementById(div_id).style.top=center_height+"px";
	
	if (show==0) {
		document.getElementById(div_id).style.visibility='visible';
	}
}

//Change the class of a specified DIV
function changeClass (id_name, class_name) {
	document.getElementById(id_name).style=class_name;
}

//Limit input fields to numbers
function numbersOnly(e, decimal) {
	var key;
	var keychar;

	if (window.event) {
		key = window.event.keyCode;
	}
	else if (e) {
		key = e.which;
	}
	else {
		return true;
	}
	keychar = String.fromCharCode(key);

	if ((key==null) || (key==0) || (key==8) ||  (key==9) || (key==13) || (key==27) ) {
		return true;
	}
	else if ((("0123456789").indexOf(keychar) > -1)) {
		return true;
	}
	else if (decimal && (keychar == ".")) { 
		return true;
	}
	else {
		return false;
	}
}