How do I stop a web page from scrolling to the top when a link is clicked that triggers JavaScript?

You need to prevent the default action for the click event (i.e. navigating to the link target) from occurring.

There are two ways to do this.

Option 1: event.preventDefault()

Call the .preventDefault() method of the event object passed to your handler. If you’re using jQuery to bind your handlers, that event will be an instance of jQuery.Event and it will be the jQuery version of .preventDefault(). If you’re using addEventListener to bind your handlers, it will be an Event and the raw DOM version of .preventDefault(). Either way will do what you need.

Examples:

$('#ma_link').click(function($e) {
    $e.preventDefault();
    doSomething();
});

document.getElementById('#ma_link').addEventListener('click', function (e) {
    e.preventDefault();
    doSomething();
})

Option 2: return false;

In jQuery:

Returning false from an event handler will automatically call event.stopPropagation() and event.preventDefault()

So, with jQuery, you can alternatively use this approach to prevent the default link behaviour:

$('#ma_link').click(function(e) {
     doSomething();
     return false;
});

If you’re using raw DOM events, this will also work on modern browsers, since the HTML 5 spec dictates this behaviour. However, older versions of the spec did not, so if you need maximum compatibility with older browsers, you should call .preventDefault() explicitly. See event.preventDefault() vs. return false (no jQuery) for the spec detail.