Update index.html

remove PromoteJS link and mention, since that site no longer exists
Merge pull request #58 from ccjjharmon/remove-PromoteJS

Update index.html
Added FireFox Addon
Merge pull request #61 from trygve-lie/firefox

Added FireFox Addon
Fix search query: filter out w3schools by url

To filter out w3schools adequately, "-inurl:w3schools.com" should be used instead of simply "-w3schools". Likely you meant to block the url, not all websites referring to w3school in their content. Like w3fools.com...

Example:

query: w3fools -w3schools
result: w3fools.com is filtered out (not what you want)

query: w3fools -inurl:w3schools.com
result: w3fools.com is the first result

Note: not tested against all available search engines, obviously. It works for Google, Yahoo and Bing, for starters.
Merge pull request #62 from bartvanandel/patch-1

Fix search query: filter out w3schools by url
Remove outdated links.

WPD is becoming the canonical resource for web dev docs. Removed the W3 doc links which have their content in WPD and the Opera Dev network link which has also succeeded to WPD's lead.

Fixes issue #63
grammar fixes in the <abbr> tag
Merge pull request #64 from APerson241/patch-1

grammar fixes in the <abbr> tag