There are lots of new feature in MS CRM 2013 and 2015 , One of them is  a  yellow color ribbon shows warning as per the use by  javascript

 Xrm.Page.ui.setFormNotification( 'Massage to be shown' );


function warning() {
    var totalamouunt = Xrm.Page.getAttribute( "new_totalamount" ).getValue();

    if (totalamouunt != null) {
        Xrm.Page.ui.setFormNotification( 'Massage to be shown' );

There are more in this like get notification for a field etc 

// clear a notification by using clearFormNotification() and use unique id .
Xrm.Page.ui.clearFormNotification( '1');

// get notification for an field
Xrm.Page.getControl( "fieldName").setNotification( "message" );

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