Why does a filter gradient on a pseudo element not work in IE8?

Question

I want to create buttons like these:

In modern browsers the effect is created using inset box-shadow and filters.
For IE8 - pseudo-elements are chosen.

Answer 1

Wow, this is a tough one.

After reviewing this chart, confirming that IE8 only likes single colons on its pseudo-elements, reading this possibly related blog article, and doing a lot of testing in jsFiddle (although, it's little in comparison to your 73?? jsFiddles), I would have to conclude that this is a bug in IE8.

IE9 can do gradients on pseudo-elements (with base64 nonsense) but IE8 is stubbornly broken.