when (msg=='OK') its only excute else part .pls help to find solution

Question

when i send msg its show only else part which is excuted even msg send sucessfully.its use ID #errormessage not #sendmessage.

success: function(msg) {

     //alert(msg);

   if(msg=='OK') {

      //msg = 'success';
      $("#sendmessage").addClass("show");
      $("#errormessage").removeClass("show");
      $('.contactForm').find("input, textarea").val("");

    }

   else {
      //msg = 'fail';
      $("#sendmessage").removeClass("show");
      $("#errormessage").addClass("show");
      $('#errormessage').html(msg);
   }

  }