function validate( form ) {
	var valid = true ;
    var fields = [ form.getElementsByTagName( "input" ), form.getElementsByTagName( "select" ), form.getElementsByTagName( "textarea" ) ] ;
    for( var i=0; i<fields.length; i++ ) {
        for( var j=0; j<fields[i].length; j++ ) {
            var field = fields[i][j] ;
            
            if( field.getAttribute( "required" ) ) {
                var label = get_label( field.getAttribute( "id" ) ) ;
                if( field.value.replace(' ','') == '' ) {
                    if( label ) {
                        label.style.color = "#f00" ;
                        label.style.fontWeight = "bold" ;
                    }
                    valid = false ;
                } else {
                    if( label ) {
                        label.style.color = "" ;
                        label.style.fontWeight = "" ;
                    }
                }
            }
        }
    }
    if( !valid ) {
        alert( alert_msg ) ;
        return false ;
    } else {
        return true ;
    }
};

function get_label( element_id ) {
    labels = document.getElementsByTagName( "label" ) ;
    for( var i=0; i<labels.length; i++ ) {
        for_elm = labels[i].getAttribute( "for" ) || labels[i].getAttribute( "htmlFor" );
        if( for_elm == element_id ) {
            return labels[i] ;
        }
    }
};