Appending/inserting in outfile.write()

[Will]

I'm trying to write a CGI Python guestbook.  Would there be a way for me
to get the script to simply append, say 14 bytes from the end, to the
HTML guestbook file rather than completely overwriting it and holding
only one entry?  I can use outfile.write to simply rewrite the entire
file.  Do I need to use another function or just set a flag?  If I can't
insert text, can i just delete the last 14 bytes and rewrite the end
from there?

Thanks,
Will