Thread:Project:Support desk/CSS bug or ?

I'm trying to change color layout. In Mediawiki:Common.css (or Vector.css) I've made some changes that work as expected. Apart from one issue. Using an in-line image works as expected:

div.vectorTabs span { background-image: url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAABkAQAAAABvV2fNAAAADUlEQVQIHWNoYBgWEACJ5TIB0K9KcAAAAABJRU5ErkJggg=="); } However, a linear-gradient is repeated all over the tab:

div.vectorTabs span { background-image: linear-gradient( #fff6f6 0%, red 100%); } What's wrong?

(MW 1.24.1 PHP 5.3.3)