A lot of Web forms (like the ones here in Tracker) allow you to submit a form, even when the submit button is not focussed, by pressing CTRL+Enter.
When you are editing a text input field, pressing Enter will normally submit a form, whereas when you are editing some fields, like text areas or the HTML Editor, pressing Enter generates a new line. So the CTRL+Enter hotkey allows easier form submission from anywhere in the form.
I haven't thought through all the consequences of this (potential conflicts, for example). I'm not sure what the equivalent Mac combination is (Command+Enter perhaps).