title: Developing a really simple browser extension
body: <p>I'm looking  to developing a browser extension.</p>
  
  <p>This extension once installed will tell the browser to include a javascript file on all page loads from a list of specific domains.</p>
  
  <p>This type of extension is called "Content Scripts" by Google Chrome.</p>
  
  <p>From what I read, to create this type of extensions for Chrome you simply put this code in 
  "Manifest" File</p>
  
  <pre><code>{
    "name": "My extension",
    ...
    "content_scripts": [
      {
        "matches": ["http://www.google.com/*"],
        "js": ["jquery.js", "myscript.js"]
      }
    ],
    ...
  }
  </code></pre>
  
  <p>Once the extension is installed jquery.js and myscripts.js will be included on every page load of google.com</p>
  
  <p>This approach to extension development adopted by Chrome seems really easy.</p>
  
  <p>My question is how difficult would it be to replicate this type of extension for the other major browsers?</p>