Cancel Form Submit - Test Page

Clicking on the submit button should bring an alert box and the form submit should be canceled. Note that Firefox submits nevertheless (the URL changes).

Clicking on the submit button should bring an alert box and the form submit should be canceled. Note that the URL doesn't change in any browser.

Thanks to Johannes Hölzl I was able to solve the problem. Clicking on the submit button now correctly cancels the form submission in every browser I tested.