title: Rails Server Error: Ruby version is 1.8.7, but your Gemfile specified 1.9.3
body: <p>I entered a existing ruby application, and type:</p>
  
  <p>$ rails s</p>
  
  <p>wanted to start rails server here.
  but it said:</p>
  
  <p>Your Ruby version is 1.8.7, but your Gemfile specified 1.9.3</p>
  
  <p>Actually, I had a 1.8.7, but I deleted it. And if I do:</p>
  
  <p>$ ruby -v</p>
  
  <p>it said:
  ruby 1.9.3p286 (2012-10-12 revision 37165) [x86_64-darwin11.4.2]</p>
  
  <p>So I don't know how can I fix it. Can you give me a help?</p>