Artifacts on CSS rendering box-shadow on Safari 6.0.2 on mountain lion

Question

I'm having some artifacts on Safari 6.0.2 on Mountain Lion on my Macbook Pro, using any other browser everything render as it is supposed to be. But curiously using Safari on my iMac with OSX Lion I can't reproduce the issue. Different OS version, different GPU, bug? or i'm doing something wrong?

Reproduction: http://jsfiddle.net/gt2g4/ and http://jsfiddle.net/T966K/1/

CSS:

#test{

    width: 150px;
    height: 150px;

    border-radius: 50%;

    background-color: blue;
    box-shadow: inset 0px 3px 0px yellow,
                inset 0px -3px 0px darkred,
                -3px -4px -0px blue;
}

About this mac:

MacBook Pro 13-inch, Mid 2012.

• Graphics Intel HD Graphics 4000 384 MB.

• Software OS X 10.8.2 (12C60).

• Safari Version 6.0.2 (8536.26.17)

Answer 1

These artifacts are now nonexistent as of OS X 10.8.3 combo update that Apple pushed March 14th, 2013.