Removing your robots.txt file doesn't effect rankings. This file is used for exclusions to tell well behaved spiders not to index files on your website. So let's say you have a download dir that you don't want to appear in G. Well the gbot will honor your robots.txt file exclusions. However a person with a little bit of knowledge can use this file against you. Since it's a text file, they simply guess where this file is placed on your website, type it into the address bar and they get to see what files you don't want people to know about. A robots.txt file is not a form of protection or security. It's merely a standard that well behaved spiders honor. phplife
It doesn't affect anything. It just gives google rules for what to search for and not to on your site.