Somewhat addresses Facepunch/garrysmod-issues#90. This could be happening to other websites loaded through a HTML/DHTML control but it won't affect most and it is fixed for the main menu.
Fixed main menu text shadow transparency on OS X.
What's with the different newlines?
There were a few trailing ones which were trimmed.
Before/After pic? I have tried that on Windows and couldn't see any noticeable differences.
Note the text shadow
Never was a bug on Windows but was one on OS X.