function checkKey(key_event)
{
    var event = key_event || window.event;

    if(!event) return;
    var key = 0;
    
    if (event.keyCode) { 
      key = event.keyCode; // IE 
    } 
    else {
      if ( typeof(event.which)!= 'undefined') { 
        key = event.which; // ff
      }
    } 
    if( key == 13 ) {
      return true;
    }
    return false;
}