10 Things to Check Before Using a CAPTCHA All CAPTCHA systems are doomed to fail. Unfortunately, this has not prevented eager developers using CAPTCHAs in even the most basic web to email forms. No one likes CAPTCHAs. They are not fun. They can not be used by everyone, such as those with impaired vision or without graphics enabled. HTML5 Cross Browser Polyfills · Modernizr/Modernizr Wiki The No-Nonsense Guide to HTML5 Fallbacks So here we're collecting all the shims, fallbacks, and polyfills in order to implant HTML5 functionality in browsers that don't natively support them. The general idea is that: We, as developers, should be able to develop with the HTML5 APIs, and scripts can create the methods and objects that should exist. Developing in this future-proof way means as users upgrade, your code doesn't have to change but users will move to the better, native experience cleanly.