1. Make sure you include the jQuery framework. - Basicly make sure the "js" folder is located at the same path as Calculator.html. The easiest way to check this is to view the document source in Firefox (right click and find view source) and try to click the link to jquery.js. If that doesn't work, your browser won't be able to find the JS file neither. Move the folder or change your path until it works.2 >>> Can I add something to this point? If, like me, you take the lazy option and use the supporting files you've downloaded from larryullman.com, make sure you change the jquery.js version number. If you're basing calculator.html on test.html, you've already done it. But the supporting files refer to 1.6.1. I couldn't figure out why my calculator submission wasn't being intercepted by jQuery, and I suddenly remembered (thanks to this post) that my jQuery version was 1.11.0. Yes, yes, I know. I shouldn't have taken the lazy option. Act in haste, repent at leisure. I'm repenting.