Fix 'Basics of HTML' broken link

The original link pointing to the Opera dev website was broken as the
document has been moved to the Webplatform site instead.

This commit fixes the link accordingly (reverts d8b7b8042c5 which removed
it entirely).
Merge pull request #2645 from vrubiolo/master

Fix 'Basics of HTML' broken link
fix bug 1051019 - Make inputs more responsive
fix bug 1050499 - Add icons for accounts
Merge pull request #2657 from darkwing/1050499-icons

fix bug 1050499 - Add icons for accounts
Merge pull request #2656 from darkwing/1051019-form

fix bug 1051019 - Make inputs more responsive
Increased the timeout for the wheel download task to help @iakshay
Added the correct persona audience to the Django settings as now required by django-allauth.
Added the correct persona audience to the Django settings as now required by django-allauth.
Prevent homepage login widget overlap on small mobile
Merge pull request #2659 from darkwing/login-widget-overlap

Prevent homepage login widget overlap on small mobile
Fix bug 1051786: Update login trouble bug template
Ensure zone image doesn't overlap title on mobile
Merge pull request #2619 from darkwing/zone-image-mobile-more

Ensure zone image doesn't overlap title on mobile
Merge pull request #2661 from openjck/1051786-trouble-logging-in-link

Fix bug 1051786: Update login trouble bug template
Merge branch 'master' into github-signup-errors
Moved error messages on signup page between label and form field.