$.extend($.expr[':'], {
    over100pixels: function(a) {
        return $(a).height() > 100;
    }
});
 
$('.box:over100pixels').click(function() {
    alert('The element you clicked is over 100 pixels high');
});

http://viralpatel.net/blogs/2009/08/20-top-jquery-tips-tricks-for-jquery-programmers.html

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