Your theme project page does not mention a specific version of CSS. Testing at http://d-theme.com/nrebuild shows the theme validates as CSS 3. Validation against CSS 2 produces the following errors.

URI : http://d-theme.com/sites/all/themes/n_rebuild/nx-style.css?s
86 tr.taxonomy-term-preview Property opacity doesn't exist in CSS level 2.1 but exists in [css3] : 0.5
90 tr.menu-disabled Property opacity doesn't exist in CSS level 2.1 but exists in [css3] : 0.5

Comments

maxrys’s picture

maxrys commented
Status: Active » Closed (fixed)

It's not a problem.
The d-theme.com - it's the problem.
The theme was tested many many times.
On the base of this theme was made many web-projects (her author).