1. $('#somebutton').click(function(){
     
   if($('#mycheck').is(':checked')){
          $('#mycheck').attr('checked',true);
   
   
      }else{
         $('#mycheck').attr('checked',false);
       }
   });
   
   
   
   
   
   
   
   
   

Ehehehehe,

When i do checked and unchecked some checkitem it not change in second time... add attr yes but not visual and real change...