- Faux columns, to get a visual stretch and make it appear that the sidebar was as long as the content https://alistapart.com/article/fauxcolumns/
- Or take that even further, with a nine-patch and 9 div's or a 3x3 table you could hack your own borders by repeating backgrounds in some axis. With CSS3 we got border-image that could help this a bit. These border styles aren't that much in favor anymore, though.
- To make rounded borders, one could use the nine-patch. But many would also use a generator to make some HTML that basically simulated a rounded border, by making lots of elements. Found this article describing it: http://benogle.com/2009/04/29/css-round-corners.html Conventional wisdom was that the added markup would be more bytes than an image would be, but less roundtrips and quite easy to do.