function listen(event, elem, func) {
    elem = getElem(elem);
    if (elem.addEventListener)  // W3C DOM
        elem.addEventListener(event,func,false);
    else if (elem.attachEvent)  // IE DOM
        elem.attachEvent('on'+event, function(){ func(new W3CDOM_Event(elem)); } );
        // for IE we use a wrapper function that passes in a simplified faux Event object.
    else throw 'cannot add event listener';
}
function getElem(elem) {
    if (document.getElementById) {
        if (typeof elem == "string") {
            elem = document.getElementById(elem);
            if (elem===null) throw 'cannot get element: element does not exist';
        } else if (typeof elem != "object") {
            throw 'cannot get element: invalid datatype';
        }
    } else throw 'cannot get element: unsupported DOM';
    return elem;
}
function W3CDOM_Event(currentTarget) {
    this.currentTarget  = currentTarget;
    this.preventDefault = function() { window.event.returnValue = false; }
    return this;
}
function toInt(cha)
{
   var X = new Array("0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F")
   var X1 = new Array("0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f")
   for(var i=0; i<16; i++)
    {
     if( cha==X[i] || cha==X1[i] ) return i
    }
   return -1 
}
function popup(url,w,h,scroll,resize,menu){
	var bal=(screen.width)?(screen.width-w)/2:100;
	var fent=(screen.height)?(screen.height-h)/2:100;
	var cucc='width='+w+',height='+h+',top='+fent+',left='+bal+',scrollbars='+scroll+',location=no,directories=no,status=no,menubar='+menu+',toolbar=no,resizable='+resize+'';
	var ablak= window.open(url, "Tamástanya", cucc);
}