Please rephrase your question, as I don't think I understand what you are asking. Are you referring to the CSS document itself or the html to which the CSS docuement is applied.
There isn't a "head" section is a CSS docuement itself. The "head" section only exists in the html.
The primary purpose of the DATA statement is to give names to constants; instead of referring to pi as 3.141592653589793 at every appearance, the variable PI can be given that value with a DATA statement and used instead of the longer form of the constant. This also simplifies modifying the program, should the value of pi change.
-- FORTRAN manual for Xerox Computers