After further checking dnnanim.gif is that little round animation that appears when you hover over a module's action menu.  And it is in the images folder. So I can only guess that the path is incorrect in the default.css file:

.LabelEditWorkClass
{
    /*background: url(/DotNetNuke/images/dnnanim.gif) no-repeat right;*/
    border: solid 0px red;
    background-color: Transparent;
}

When I delete the above background line out of the default.css file the file not found error goes away.  I will log into Gemini since you told me to Sebastian.