var t;			
	t = 0.8;
	
	function changerTaille(modif) {
		t = t + modif;
		document.getElementsByTagName("body")[0].style.fontSize = t + "em"; 
               if ( t >= "1" )
                  {
                       document.getElementsByTagName("body")[0].style.fontSize = 1 + "em";
                       t=1;
                   }
                if ( t <= "0.6" )
                  {
                       document.getElementsByTagName("body")[0].style.fontSize = 0.6 + "em";
                       t=0.6;
                   }               
		}