Where is sidebarsplitter.png?

In the CSS for a Multiscreen HTML5 layout, it refers to a file named "sidebarsplitter.png," but I searched my entire C:\ drive for it and there is no such file.

In layout.css for the "social" layout:

div.socialbuttons {

                   width:95%;

                   text-align:left;

                   margin:10pt 2.5% 15pt;

                   background:transparent url("sidebarsplitter.png")      repeat-x left bottom;

                   padding-bottom:5px;

}

(Also, the Facebook "like" button in the "social" layout does not apper in the editor or in the generated help.)

The Multiscreen stuff seems to have been rushed to release. I hope there will be an update soon, because the HTML5 layouts are pretty cool (after being tweaked a bit).