var myvar;
function menuinit() {
        document.getElementById('m1').style.display = 'none';
		document.getElementById('pm1').src = 'images/plus.png';
}
function menuexpand (i) {
        menuinit();
        if (myvar == i) {
		document.getElementById('p' + i).src = 'images/plus.png';
		document.getElementById(i).style.display = 'none';
		myvar = '';
	}
        else {
		document.getElementById('p' + i).src = 'images/minus.png';
		document.getElementById(i).style.display = 'block';
		myvar = i;
	}
}
<!--
if (document.images)
{
  pic1= new Image(15,15); 
  pic1.src="images/plus.gif"; 
  pic2= new Image(15,15); 
  pic2.src="images/minus.gif"; 

}
//-->