Help Understanding Browser Differences

Here is the java script, it is called as an event when i click the submit button on a form.

<!–
var browser = navigator.appName;
var version = parseFloat(navigator.appVersion);

function Validate(id)
{
document.writeln(browser);
}

–>
When I click the submit button on my form in Explorer 7 it works, however, when I do it in Firefox it does not work. Why is this?

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