Automatically Change Html Attributes On Page Load

I am trying to create a Google Chrome custom theme (an image displayed on the new tab page). However there are these little last visited boxes blocking out part of the image, and t

Solution 1:

in your manifest.json

"permissions": ["<all_urls>"],
"content_scripts": [
    {
    "matches": [
        "http://*/*",
        "https://*/*"
        ],
    "js": ["content.js"],
    "run_at": "document_end"         // pay attention to this line
    }
],

and in your content.js

(function(window, chrome){
  "use strict";
  var doc = window.document;
  doc.getElementById("mv-tiles").style.opacity = "0";
}(window, chrome));