My title and description is mission IN SERP'S from the last three days.. while checking cache, it is saying "Requested url doent found on server" I am not sure about the reason...

But i just checked the robots.txt file

Can any pls explain what is this

User-agent: *
Allow: /


Is that mean to crawl all the pages including homepage...For example My website is www.abc.com and when you will open