No, the code in that thread was correct, you implemented it incorrectly. This is broken:
<img src="{$ImagesDir}/free_shipping.gif" /</span>
To be W3C compliant, an image tag needs to be closed with the / at the end (as does any tag with no closing tag) and the alt tag is also required. ALT text is for people with disabilities, so it would also be wise to put 'Free shipping' in the alt tag.