All SAIC Students have full access to Lynda.com tutorials (normally a paid membership). TAKE ADVANTAGE!
This tutorial is a good explanation of when to use Div and Span
http://www.lynda.com/CSS-tutorials/Apply-styles-SPAN-DIV/47543/55246-4.html
To Access your Lynda.com go to this SAIC site:
http://www.saic.edu/academics/computing/lyndaonlinesoftwaretraining/