Improved HTTP cache, removed outdated code

HTTP cache related to update date
Commented inline favicon option to save the file size
Removed meta isFamilyFriendly
Removed outdated code
Fixed prevention of XSS and SQL injection
Margin after heading
HTTP cache related to update date
$mysqli as a global

Fixed error: Call to a member function prepare() on a non-object
HTTP cache related to relevant update date
Fixed assets source, HTTP cache related to relevant update date
Increased cache, removed HTTP Expires

Increased cache from 1 hour to 1 day
Removed needless HTTP header Expires
Updated Google Webmaster links
Better typography style and form compatibility

Improved typography style
Improved form elements compatibility