// Manage element display
function displayElement(name,display,content){
   var element=document.getElementById(name);
   var left=(document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft)+(window.innerWidth/2-parseInt(element.style.width)/2);
   var top=(document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop)+(window.innerHeight/2-parseInt(element.style.height)/2);
   element.style.left=(left>0 ? left : 0)+"px";
   element.style.top=(top>0 ? top : 0)+"px";
   if(content!=null){
       element.innerHTML=content; // element must be a div for IE innerHTML
   }
   element.style.display=display;
}

// Manage display
var show=new Array();
function hideOrShow(element){
   if(!show[element]){
       displayElement(element,"block");
       show[element]=true;
   }
   else{
       displayElement(element,"none");
       show[element]=false;
   }
}