Chrome Extension Manifest 'Matches'

You need to surround the value of the content_scripts field in square brackets:

"content_scripts": [ {
  "matches": ["http://*"],
  "js": ["scripts.js"]
} ]

(see the Chrome Docs for more info)

Incidentally, using http://*/* would be a better match for all urls (see the docs), adding https://*/* if you also need to match those as well.

Edit:

Following your edit, the error you are getting is because of the match pattern being incorrect.

If you want to match every URL, then Google has a special pattern just for this purpose: <all_urls>

Sample usage:

"matches": ["<all_urls>"],

See this page for more info: https://developer.chrome.com/extensions/match_patterns