Well, the Diagram or Comment I put it in uses neither. If there would be a z-index on the container <div> that puts it behind the Comment background, the latter could block the view. But I made the background of the <div> that contains the entire Diagram green, and it is clearly in front of the Comment background. But the green doesn't show through the board squares, even if I can see that these are partly transparent.
I used the FireFox inspect function to see what attributes the container <div> HTML element has, and this looks fine. It has both a blue backgroundColor and a backgroundImage, and it shows a demagnified image of the board image when I hover over the link, so I know the URL is OK.
Could it be float or z-index related?
Well, the Diagram or Comment I put it in uses neither. If there would be a z-index on the container <div> that puts it behind the Comment background, the latter could block the view. But I made the background of the <div> that contains the entire Diagram green, and it is clearly in front of the Comment background. But the green doesn't show through the board squares, even if I can see that these are partly transparent.
I used the FireFox inspect function to see what attributes the container <div> HTML element has, and this looks fine. It has both a blue backgroundColor and a backgroundImage, and it shows a demagnified image of the board image when I hover over the link, so I know the URL is OK.