I will show you how to create a ASP.NET Captcha control without using any HTTP HANDELRS or what so ever. you can easily plug it into your web pages.
a = 2 + 3 (where 2 and 3 are 2 random numbers)
Session("Answer") = 5
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions.
Consider email address RFCs:
Look at HTML5 form input element (with type=email) regex pattern: