$(function($) {

    // external
    $.fn.external = function() {
        return this.each(function(){ this.target = '_blank'; });
    };
    $('a[rel=external]').external();


    // rollover
    var CLASS_NAME = "btn";
    var SUFFIX     = "_o";
    $.fn.rollover = function() {
        return this.each(function() {
            this.orig_src = this.src;
            this.ol_src   = this.src.replace(/(?:_sel)?\.(gif|jpg|png)/, SUFFIX+'.$1');
            document.createElement("img").src = this.ol_src;
            $(this).hover(
                function() { this.src = this.ol_src; },
                function() { this.src = this.orig_src; }
            );
        });
    };
    $("img."+CLASS_NAME+", input."+CLASS_NAME).rollover();

});