$(function() {

// Creating custom :external selector
$.expr[':'].external = function(obj){
    return !obj.href.match(/^mailto\:/)
            && (obj.hostname != location.hostname);
};

// Add 'external' CSS class to all external links
$('a:external').addClass('external');

$('.external').click(function() { 
    return confirm("This link leads offsite. \n We are not responsible for offsite content."); 
});

});