title: How to get user's id by user's profile url?
body: <p>Now when the user input his personal profile url to a textbox, such as <a href="http://www.facebook.com/Google" rel="nofollow">http://www.facebook.com/Google</a>.
  The form immediately show the Google logo(it's the Google's facebook paeg's logo).</p>
  
  <p>If I know the page id,I can show the Google logo in this way:</p>
  
  <p>http://graph.facebook.com/[USER_ID]/picture</p>
  
  <p>But how to know the user id with any api?</p>