fetch_title.js

// query: select * from html where url="http://some.url.com" and xpath='//title'
var yql_url = "http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20html%20where%20url%3D%22" + encodeURIComponent(url) + "%22%20and%0A%20%20%20%20%20%20xpath%3D'%2F%2Ftitle'&format=json&callback=?";

$.getJSON(yql_url, function(json) {
  if (json && json.query && json.query.results && json.query.results.title) {
    $('#page_title').html(json.query.results.title);
  }
});