Manifest

{
  "name": "Omegle",
  "version": "0.1",
  "description": "Omegle",
  "icons": { "16": "icon16.png",
			 "48": "icon48.png",
			 "128": "icon128.png",
		     "default": "icon128.png"},
  "content_scripts": [
    {
      "matches": ["http://omegle.com/*", 
				  "http://cardassia.omegle.com/*", 
				  "http://bajor.omegle.com/*", 
				  "http://promenade.omegle.com/*"],
      "js": ["jquery-1.6.4.js", "script.js"],
      "all_frames": true
    }
  ]
}

Content Script
window.frames[0].document.getElementById('startachat').innerText = "CHANGED !";