Message Background Javascript Not working as Well

As well as the name color, my background javascript has seemed to stop working, unless iv screwd the script up somehow

Code:

$(function() {
 customBg('Spyro ▀█▀ Dragon', 'Spyro-background', 'http://i19.servimg.com/u/f19/16/87/57/90/spyro_10.jpg');
 
  function customBg(name, classname, image) {
    var ua = window.navigator.userAgent, td = 'td', pos = '';
    $('.post:has(.name:contains('+name+'))').addClass(classname);
    if (ua.match(/Chrome/)) td = 'td:last-child', pos = '140% 0';
    if (ua.indexOf('MSIE ') > 0 || ua.match(/Trident/) || ua.match(/Chrome/)) $('head').append('<style type="text/css">.post.'+classname+' > '+td+' { background:none }.post.'+classname+' {background: url('+image+') no-repeat '+pos+' transparent }</style>');
    else $('head').append('<style type="text/css">.post.'+classname+' td { background:none }.post.'+classname+' {background: url('+image+') no-repeat center center / 100% 100% transparent }</style>');
  }
});

Hello @SpyroDragon

it seems that the code works correctly and that there are no errors in de syntax

Have you installed other javascripts before this one?