Sets or replaces the content of the document. If the document is an HTML
document the content is everything after the BODY tag. Information
from the HEAD and BODY tag is in the stored in the object record.
If you provide this information in the content of the document too,
the Hyperwave server will change the object record accordingly when
the document is inserted. Probably not a very good idea.
If this functions fails the document will retain its old content.