Strange. The HTML <div> element that contained the Diagram had a style property that specified aava.png as background image. I made that Diagram, but I cannot recall having put that there, and I have no idea what the aava.png could have depicted. If I want a background for the Diagram, there is the parameter background=... for this, but that would only put the specified URL in the diagram it creates after the page gets loaded (and for the <table> tag that defines the board), and this was in the page source. The only explanation I can think of is that I used an existing <div> element when inserting the Diagram.
Strange. The HTML <div> element that contained the Diagram had a style property that specified aava.png as background image. I made that Diagram, but I cannot recall having put that there, and I have no idea what the aava.png could have depicted. If I want a background for the Diagram, there is the parameter background=... for this, but that would only put the specified URL in the diagram it creates after the page gets loaded (and for the <table> tag that defines the board), and this was in the page source. The only explanation I can think of is that I used an existing <div> element when inserting the Diagram.
Anyway, I removed that background style now.