var OpenLinks = new Class({
    //initialization

    initialize: function(file_extensions,override_targets,target,no_class) {

        //analyze all anchors
        $$('a').each(function(el) {

        //check each href for case-insensitive file extensions
        var str = el.get('href');
        var ext = str.substring(str.lastIndexOf('.') + 1,str.length)
        if(file_extensions.contains(ext.toLowerCase()) && ((override_targets || !el.get('target')) && !el.hasClass(no_class + '')))
        {
            el.setProperty('target',target ? target : '_blank');
        }
        });
    }
});