Transparent shapes not transparent in HTML5?

Hi, is it just me or is there an issue with transparent shapes when publishing to HTML5.

I had an image with a transparent box on top containing a hyperlink. Since the background of my page was dark grey I immediately spotted the transparent box after publishing and checking the HTML5 output. It's color was just a fraction lighter then my background color showing clearly there was a big box on top of my image :( 

I tried with a textbox on which I put a hover state and the same thing happend. 

Is this default HTML5, unable to deal with transparancy or an actual bug I should report?

Jeff

seriouslearning.nl