This javascript cut & paste code snippet will allow an e-mail address validation function. It allows the usual user@domain syntax in addition allows user@ip number format as well as "User with Spaces"@domain or ip number.  All of which are legal syntax according to W3C. It also checks that the user hasn't done anything wrong like having multiple @'s or multiple placements in the address (e.g. craig@j@x.com and craig@j..x.co.uk)

Insert this code into your HEAD of HTML

<!-- // == This Script Free To Use Providing This Notice Remains == // // == This Script Has Been Found In The http://www.DesignerWiz.com Javascript Public Archive Library == // // == NOTICE: Though This Material May Have Been In A Public Depository, Certain Author Copyright Restrictions May Apply == // --><script language="JavaScript" type="text/javascript"> <!-- Original: Sandeep V. Tamhankar (stamhankar@hotmail.com) --> <!-- This script and many more are available free online at --> <!-- The JavaScript Source!! http://javascript.internet.com --> <!-- Begin function emailCheck(emailStr) { // checks if the e-mail address is valid var emailPat = /^(\".*\"|[A-Za-z]\w*)@(\[\d{1,3}(\.\d{1,3}){3}]|[A-Za-z]\w*(\.[A-Za-z]\w*)+)$/; var matchArray = emailStr.match(emailPat); if (matchArray == null) { alert("Your email address appears to be incorrect. Please re-check address and resubmit. (check the '@' and '.'s in the email address)"); return false; } // make sure the IP address domain is valid var IPArray = matchArray[2].match(/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/); if (IPArray != null) { for (var i=1;i<=4;i++) { if (IPArray[i]>255) { alert("Destination IP address is invalid!") return false; } } } return true; } // End --> </script>

Insert this code into your BODY section

<center> <form name=emailform onSubmit="return emailCheck(this.email.value);"> Your Email Address: <input type=text name="email" class="hexfield"><br> <input type="submit" value="Submit" class="hexfield1"> </form> </center>

Simply Cut and Paste Script code
Be sure to properly place script position in HEAD & BODY sections of html 

This script has been in the DesignerWiz.com Public Library.