If your content is loaded in dynamically (like if you are using a CMS system), then it gets loaded after Selectivizr is run, and therefore it won't work.
From selectivzr.com:
The emulation is not dynamic. Once the styles are applied they are fixed so changes to the DOM won't be reflected.
I recommend using Modernizr instead. You can check for css-lastchild
and customize the styles if the browser doesn't support it (together with the rest of the CSS3 selectors, like nth-child
, etc.). I share your pain though!