var ns4 = (document.layers)? true:false;   //NS 4   
var ie4 = (document.all)? true:false;   //IE 4
var dom = (document.getElementById)? true:false;   //DOM 


function presentation(id1){
	if (dom) {
		document.getElementById(id1).style.visibility = "hidden";
		}
		else if (ie4) {
			document.all[id1].style.visibility = "hidden";
			}
			else if (ns4) {
				document.layers[id1].visibility = "hidden";
				}
				
}


function services(id1){
	if (dom) {
		document.getElementById(id1).style.visibility = "visible";
		}
		else if (ie4) {
			document.all[id1].style.visibility = "visible";
			}
			else if (ns4) {
				document.layers[id1].visibility = "visible";
				}
				
}

function services2(id1){
	if (dom) {
		document.getElementById(id1).style.visibility = "hidden";
		}
		else if (ie4) {
			document.all[id1].style.visibility = "hidden";
			}
			else if (ns4) {
				document.layers[id1].visibility = "hidden";
				}
				
}


function tarifs(id1){
	if (dom) {
		document.getElementById(id1).style.visibility = "hidden";
		}
		else if (ie4) {
			document.all[id1].style.visibility = "hidden";
			}
			else if (ns4) {
				document.layers[id1].visibility = "hidden";
				}
				
}


function acces(id1){
	if (dom) {
		document.getElementById(id1).style.visibility = "hidden";
		}
		else if (ie4) {
			document.all[id1].style.visibility = "hidden";
			}
			else if (ns4) {
				document.layers[id1].visibility = "hidden";
				}
				
}

function liens(id1){
	if (dom) {
		document.getElementById(id1).style.visibility = "hidden";
		}
		else if (ie4) {
			document.all[id1].style.visibility = "hidden";
			}
			else if (ns4) {
				document.layers[id1].visibility = "hidden";
				}
				
}

function contact(id1){
	if (dom) {
		document.getElementById(id1).style.visibility = "hidden";
		}
		else if (ie4) {
			document.all[id1].style.visibility = "hidden";
			}
			else if (ns4) {
				document.layers[id1].visibility = "hidden";
				}
				
}
function centrerpopup(page,largeur,hauteur,options) {
			 var top=(screen.height-hauteur)/2;
			 var left=(screen.width-largeur)/2;
			 window.open(page,"","top="+top+",left="+left+",width="+largeur+",height="+hauteur+","+options);
			 }