Firefox' about:conf tricks + Bonus extension

Spell Check Single Line Fields

In address bar type: about:config.
In the “Filter” field type layout.spellcheckDefault.
As you can see it has value of "1". Double click on it and enter 2 as its new value.
Restart firefox.

Address bar as Search BOX
Yes in Mozilla Firefox you can just type your search query in address bar and get the search results displyed to you!
For this:

Type about:config in address bar of Mozilla Firefox.
Type keyword.URL in filter box.
Right-Click on that line and select modify option.
Enter any of the following string for corresponding search engine!(Google's Feeling lucky is my favorite, and it's by default)

Google: Feeling Lucky - http://www.google.com/search?ie=UTF-8&oe=UTF-8&sourceid=navclient&gfns=1&q=
Vanilla Google - http://www.google.co.in/search?btnG=Google+Search&q=
Wikipedia - http://en.wikipedia.org/wiki/Special:Search?fulltext=Search&search=
Wikipedia: Feeling Lucky - http://en.wikipedia.org/wiki/Special:Search?go=Go&search=
Yahoo - http://search.yahoo.com/search?p=

(Default Firefox en-US keyword URL: http://www.google.com/search?ie=UTF-8&oe=UTF-8&sourceid=navclient&gfns=1&q=)

For those of you who viewing pages with some Cyrillic in address
Для тех у кого возникают проблемы с копированием ссылок с кириллицей в Firefox.