function checkEnter(e){         //e is event object passed from function invocation

         var characterCode;// literal character code will be stored in this variable

         if(e && e.which){ //if which property of event object is supported (NN4)
              e = e
              characterCode = e.which //character code is contained in NN4's which property
         }else{
               e = event
               characterCode = e.keyCode //character code is contained in IE's keyCode property
         }

         if(characterCode == 13){ //if generated character code is equal to ascii 13 (if enter key)
                          document.forms[0].submit() //submit the form
                          return false
         }else{
               return true
         }

}