5
After some research: yes, you can use CSS and divs to achieve that
http://www.alistapart.com/articles/customcorners/
http://www.alistapart.com/articles/customcorners2/
http://www.vertexwerks.com/tests/sidebox/
http://interface-7.net/20040218/
http://www.cubedonline.com/newdesign/index.html
http://www.markschenk.com/cssexp/roundedbox/arrows.html
http://www.redmelon.net/tstme/4corners/
Much more elegant than tables, much more likely to trigger rendering bugs too