Several readers have commented that the HTML calculated column works fine in the list view, but not when displaying a single item.
Single items are displayed in a page called DispForm.aspx. If you want the HTML to render in this page, you need to add the script there too.
Some of you may reply that there is no “Edit page” option in DispForm.aspx. In this case, you need to use the trick described on the CEWP post. This is easy, but note that it is not supported by Microsoft.
Hope this helps!