function ouvrir (){  mafen=window.open("plan.html","lol","width=450px,height=400px");}function ouvrir2 (){  mafen=window.open("plan2.html","lol","width=450px,height=400px");}function ouvrir3 (){   mafen=window.open("plan3.html","lol","width=450px,height=400px");}