Say you are an up and coming web developer. You want to make a web app that can access content on other sites. Perhaps you want to make a word cloud from a news article on BBC. Or you want to see what videos a site has embedded within itself. You could achieve that by doing some server side voodoo. The ‘standard’ way to go about it would be to download the site to your server and then serve its contents to your webpage.  But that would require two things: