To work with jQuery version above 1.9.x
HTML
The html markup as shown above:
<ul>
<li>Go to the store</li>
<li>Pick up dinner</li>
<li>Debug crash</li>
<li>Take a jog</li>
</ul>
JS
Use preventDefault() instead of return false which doesn't kill any other handlers you might have
$('li').on('selectstart', function (event) {
event.preventDefault();
});
Example: jsFiddle