if (document.images) {

//rollovers
		a = new Image();
		a_down = new Image();
		b = new Image();
		b_down = new Image();
		c = new Image();
		c_down = new Image();
//		psychology = new Image();
//		psychology_down = new Image();
		d = new Image();
		d_down = new Image();
		e = new Image();
		e_down = new Image();
		f = new Image();
		f_down = new Image();

		a.src = "imagenesindices/a0.gif"; 		a_down.src = "imagenesindices/a1.gif"; 		b.src = "imagenesindices/b0.gif"; 		b_down.src = "imagenesindices/b1.gif"; 		c.src = "imagenesindices/c0.gif"; 		c_down.src = "imagenesindices/c1.gif"; 		d.src = "imagenesindices/d0.gif"; 		d_down.src = "imagenesindices/d1.gif"; 		e.src = "imagenesindices/e0.gif"; 		e_down.src = "imagenesindices/e1.gif"; 		f.src = "imagenesindices/f0.gif"; 		f_down.src = "imagenesindices/f1.gif";

}

function buttonOn(imageName) {
	if (document.images) {
		document[imageName].src = eval(imageName+"_down.src")
		}
	}

function buttonOff(imageName) {
	if (document.images) {
		document[imageName].src = eval(imageName+".src")
		}
	}