var aryClassElements1 = new Array();
var aryClassElements2 = new Array();

function getElementsByClassName( strClassName1, strClassName2, obj ) {
    if ( obj.className == strClassName1 ) {
        aryClassElements1[aryClassElements1.length] = obj;
    }
	if ( obj.className == strClassName2 ) {
        aryClassElements2[aryClassElements2.length] = obj;
    }	
    for ( var i = 0; i < obj.childNodes.length; i++ )
        getElementsByClassName( strClassName1, strClassName2, obj.childNodes[i] );
}

function grabtheclass() {
    aryClassElements1.length = 0;
	aryClassElements2.length = 0;
    getElementsByClassName( 'main', 'sidebar', document.body );
    for ( var i = 0; i < aryClassElements1.length || i < aryClassElements2.length; i++ ) {
		if(aryClassElements1[i].offsetHeight > aryClassElements2[i].offsetHeight)
		{
			aryClassElements2[i].style.height = aryClassElements1[i].offsetHeight +'px';
		}
		else if (aryClassElements1[i].offsetHeight < aryClassElements2[i].offsetHeight)
		{
			aryClassElements1[i].style.height = aryClassElements2[i].offsetHeight +'px';
		}
	}
}