function isblank(s) {
   for (var i = 0; i < s.length; i++) {
        var c = s.charAt(i);
        if ((c !=' ') && (c != '\n') && (c != '\t'))
        return false;
   }
   return true;
}

function validateForm() {

if( (document.form1.firstname.value =="") ||
      (document.form1.firstname.value == null) ||
           isblank(document.form1.firstname.value) )
   {
      alert("Please enter your first name");
      return false;
   }
 else if ( (document.form1.surname.value =="") ||
           (document.form1.surname.value == null) ||
           isblank(document.form1.surname.value) )
   {
      alert("Please enter your surname");
      return false;
   }
 else if ( (document.form1.address1.value =="") ||
           (document.form1.address1.value == null) ||
           isblank(document.form1.address1.value) )
      {
         alert("Please enter your address");
         return false;
   }
  else if ( (document.form1.town.value =="") ||
            (document.form1.town.value == null) ||
            isblank(document.form1.town.value) )
    {
       alert("Please enter your town");
       return false;
   }
  else if ( (document.form1.postcode.value =="") ||
               (document.form1.postcode.value == null) ||
               isblank(document.form1.postcode.value) )
       {
          alert("Please enter your Postcode");
          return false;
   }
  else if ( (document.form1.email.value =="") ||
            (document.form1.email.value == null) ||
            isblank(document.form1.email.value) )
       {
          alert("Please enter your Email Address");
          return false;
    }
  else if ( checkMail()==false )
           {
              alert("Please enter a valid Email Address");
              return false;
    }
 else {
   return true;
   }
 }
 
 function checkMail()
 {
 	var x = document.forms[0].email.value;
 	var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
 	if (filter.test(x)){ 
 		return true;
 	}else{ 
 		return false;
 	}
 }