function showError (field, img) {
   field.className = 'error';
   img.src = '/img/x.png';
}

function showAccept (field, img) {
   field.className = '';
   img.src = '/img/check.png';
}

function checkData (frm, userMin, userMax, passMin, passMax) {
   errMsg = '';

   //value = frm.elements['username'].value;
   var userName = document.getElementById('RegisterUsername');
   var userNameImg = window.document.getElementById('username_img');
   if (userName.value == '') {
      errMsg = errMsg + '\n * Username is required';
      showError(userName, userNameImg);
   }
   else if (userName.value.length < userMin) {
      errMsg = errMsg + '\n * Username is too short';
      showError(userName, userNameImg);
   }
   else if (userName.value.length > userMax) {
      errMsg = errMsg + '\n * Username is too long';
      showError(userName, userNameImg);
   }
	else if (userName.value.match(/[^a-zA-Z0-9]/)) {
		errMsg = errMsg + '\n * Username can only contain letters and numbers';
		showError(userName, userNameImg);
	}
   else {
      showAccept(userName, userNameImg);
   }
   
   var userPass1 = document.getElementById('RegisterPasswd');
   var userPass2 = document.getElementById('RegisterPasswdAgain');
   var userPass1Img = window.document.getElementById('password_img');
   var userPass2Img = window.document.getElementById('passwordagain_img');
   if (userPass1.value == '' && userPass2.value == '') {
      errMsg = errMsg + '\n * Password is required';
      showError(userPass1, userPass1Img);
      showError(userPass2, userPass2Img);
   }
   else if (userPass1.value.length < passMin) {
      errMsg = errMsg + '\n * Password is too short';
      showError(userPass1, userPass1Img);
   }
   else if (userPass1.value.length > passMax) {
      errMsg = errMsg + '\n * Password is too long';
      showError(userPass1, userPass1Img);
   }
   else if (userPass1.value != userPass2.value) {
      errMsg = errMsg + '\n * Passwords do not match';
      showError(userPass1, userPass1Img);
      showError(userPass2, userPass2Img);
   }
	 else {
	 		showAccept(userPass1, userPass1Img);
			showAccept(userPass2, userPass2Img);
	 }
   
   var userEmail = document.getElementById('RegisterEmail');
   var userEmailImg = window.document.getElementById('email_img');
   if (userEmail.value == '') {
      errMsg = errMsg + '\n * Email address is required';
      showError(userEmail, userEmailImg);
   }
   else if (!isEmail(userEmail.value)) {
      errMsg = errMsg + '\n * Email address is not valid';
      showError(userEmail, userEmailImg);
   }
	 else {
	 		showAccept(userEmail, userEmailImg);
	 }
   
   if (errMsg != '') {
      errMsg = 'There was a problem with your registration:' + errMsg;
      errMsg = errMsg + '\nPlease correct this problem and try again.';
      alert(errMsg);
      return false;
   }
   return true;
}