Edit in JSFiddle

//Do it with jQuery
var linkJPG = $('a[href$=.jpg]');
var linkZIP = $('a[href$=.zip]');
var linkPDF = $('a[href$=.pdf]');

//    linkJPG.click(function(){
//        var linkname = $(this).attr('title') || 'file';
        //pageTracker._trackPageview('/jpg/downloads/' + linkname);
//        alert('downloads/' + linkname);
//    });


if(linkJPG == "") { 
} else {
    linkJPG.click(function(){ 
        var linkname = $(this).attr('title') || 'file';
//        pageTracker._trackPageview('/jpg/downloads/' + linkname);
        alert('downloads/' + linkname);
    });
};
if(linkZIP == "") {
} else {
    linkZIP.click(function(){
        var linkname = $(this).attr('title') || 'file';
//        pageTracker._trackPageview('/jpg/downloads/' + linkname);
        alert('downloads/' + linkname);
    });
};
if(linkPDF == "") {
} else {
    linkPDF.click(function(){
        var linkname = $(this).attr('title') || 'file';
//        pageTracker._trackPageview('/jpg/downloads/' + linkname);
        alert('downloads/' + linkname);    
    });
};   
/*
Do it with Mootools
var linkJPG = $$('a[href$=.jpg]');
var linkZIP = $$('a[href$=.zip]');
var linkPDF = $$('a[href$=.pdf]');


if(linkJPG == "") { 
} else {
    linkJPG.addEvent('click', function(){
        var linkname = this.getProperty('title') || 'file';
        pageTracker._trackPageview('/downloads/');
        alert('/downloads/' + linkname);
    });
};

if(linkZIP == "") {
} else {
    linkZIP.addEvent('click', function(){
        var linkname = this.getProperty('title') || 'file';
        pageTracker._trackPageview('/downloads/');
        alert('/downloads/' + linkname);
    });
};

if(linkPDF == "") {
} else {
    linkPDF.addEvent('click', function(){
        var linkname = this.getProperty('title') || 'file';
        pageTracker._trackPageview('/downloads/');
        alert('/downloads/' + linkname);
    });
};
*/

/*
//Code explained
//Find the href ending in .pdf and add Google Page Tracker
$$('a[href$=.pdf]').addEvent('click', function(){
    pageTracker._trackPageview('/pdf/downloads/');
});
*/

<a href="http://i41.tinypic.com/2uhsoef.jpg" title="#1" target="_blank">Link to a JPG</a> | 
 <a href="http://itracedesigns.com/downloads/moo-tooltip-042610.pdf" target="_blank">Link to a PDF</a> |

 <a href="http://itracedesigns.com/downloads/moo-tooltip-042610.zip" target="_blank">Link to a ZIP</a> |

 <a href="http://i28.tinypic.com/20rjq1d.jpg" target="_blank">Link to a JPG</a> |

 <a href="http://google.com" target="_blank">Link to a page</a>