function popupCentre(txtPage,nbLargeur,nbHauteur,txtOption){
	var nbTop=(screen.height-nbHauteur)/2;
	var nbLeft=(screen.width-nbLargeur)/2;
	var winPopup=window.open(txtPage,"","top="+nbTop+",left="+nbLeft+",width="+nbLargeur+",height="+nbHauteur+","+txtOption);
}
function normalPosition()
{
document.getElementById('block_specialites').style.backgroundPosition="0px 0px";
}
function rollToitures()
{
document.getElementById('block_specialites').style.backgroundPosition="0px -528px";
}
function rollBassins()
{
document.getElementById('block_specialites').style.backgroundPosition="0px -1056px";
}
function rollTerrasses()
{
document.getElementById('block_specialites').style.backgroundPosition="0px -1584px";
}
// La fonction qui affiche/masque l'élément 
function bascule(elem)
{
// Quel est l'état actuel ?
etat=document.getElementById(elem).style.visibility;
if(etat=="hidden"){document.getElementById(elem).style.visibility="visible";}
else{document.getElementById(elem).style.visibility="hidden";}
}