Added lighter background for USP page and created links for each section

Signed-off-by: Stephen Elford <steve@trafficwebsites.co.uk>
Images and videos buttons were the wrong way round.

Signed-off-by: Stephen Elford <steve@trafficwebsites.co.uk>
Changed button background to CSS, added active state and globalised transition speed.

Signed-off-by: Stephen Elford <steve@trafficwebsites.co.uk>