var col1 = document.getElementById("menu");
var col2 = document.getElementById("contenu");
var col3 = document.getElementById("dossiers");
var taille1 = col1.offsetHeight;
var taille2 = col2.offsetHeight;
var taille3 = col3.offsetHeight;

if(taille2 > taille3 && taille2 > taille1) {
	col3.setAttribute("style", "height: " + eval(taille2) + "px");
	col1.setAttribute("style", "height: " + eval(taille2) + "px");
	if (document.all) { 
		col3.style.setAttribute("cssText", "height: " + eval(taille2) + "px");
		col1.style.setAttribute("cssText", "height: " + eval(taille2) + "px");
	}
}
else if(taille1 > taille2 && taille1 > taille3) {
	col2.setAttribute("style", "height: " + eval(taille1) + "px");
	col3.setAttribute("style", "height: " + eval(taille1) + "px");
	if (document.all) { 
		col2.style.setAttribute("cssText", "height: " + eval(taille1) + "px");
		col3.style.setAttribute("cssText", "height: " + eval(taille1) + "px");
	}
}
else if(taille3 > taille1 && taille3 > taille1) {
	col1.setAttribute("style", "height: " + eval(taille3) + "px");
	col2.setAttribute("style", "height: " + eval(taille3) + "px");
	if (document.all) { 
		col1.style.setAttribute("cssText", "height: " + eval(taille3) + "px");
		col2.style.setAttribute("cssText", "height: " + eval(taille3) + "px");
	}
}