function check_form()
    {
     if(document.form.name.value == "")  {
       alert("Please enter your name !");
       document.form.name.focus();
       return false;
      }
     if(document.form.email.value == "") {
       alert("Please enter your email !");
       document.form.email.focus();
       return false;
      }
     if(document.form.email.value.indexOf('@') == -1) {
       alert("Please enter a valid email");
       document.form.email.focus();
       return false;
      }
     if(document.form.subject.value == "") {
       alert("Please enter a subject");
       document.form.subject.focus();
       return false;
      }
     if(document.form.message.value==""){
         alert("Please enter a message !");
         document.form.message.focus();
         return false;
     }
    }