function hoverable(hoverElement, destination) {

$(hoverElement).hover(function(){
      $(destination).addClass('hovered');
      return true;
   },
   function(){
      $(destination).removeClass('hovered');
      return true;
   }
   );

}

$(document).ready(function(){
   hoverable('#main_hover_left','#main_background_left');
   hoverable('#main_hover_right','#main_background_right');
   
   $('#main_background_left').click(function(){
      window.location = 'http://kros-system.pl/offer/wood';
   });
   
   $('#main_background_right').click(function(){
      window.location = 'http://kros-system.pl/offer';
   });
});