Create main.css

The base CSS for all pages (Work In Progress)
Added a comment to main.css
Moved css from index.html to main.css and modified it.
Made navigation bar fixed, formatted some code, etc...
Fixed a console error
Fixed gap between corner of page and navigation bar!
Cleaned CSS of not needed changes and fixed colour codes(line 18 and 24 of index.html)
More CSS changes
Merge pull request #1 from DM5555/master

CSS merge