will it affect your ranking after your site is finally up to date and it re-indexes it?... I forgot to create a robot.txt file for one of my sites and despite having backlinks, it is very low in the SERPS and I think this is because the bots visited when I had partial content... and despite having full related content now it hasn't moved up much... it's about a month old. anyone know? thanks.
Not having a robots.txt file won't hurt your rankings. Quality backlinks and time is what you need. A month is not nearly enough time to expect to start ranking well in google. Give it six months to a year.