Update _768up.less

I was working with bones and found a small error under navigation, 'li.current-page-ancestor' should be 'li.current_page_ancestor' (2 occurrences).

I am new to programming, learning to make wordpress themes. :)
added flush_rewrite_rules on Theme switch
Replace HTML comments by PHP comments

That way they don't appear in production sources.
Fix accessibility issue in the menu and cleaned up some CSS.
Fix article footer class of single-custom-type.php
Merge pull request #486 from Silex/master

Replace HTML comments by PHP comments
Merge pull request #477 from cfoellmann/flush

added flush_rewrite_rules on Theme switch
Merge pull request #493 from alexgarces/patch-1

Fix article footer class of single-custom-type.php
Fix header nav style

there is no ul.nav in the HTML.
fix classname li.current_page_ancestor

It was li.current-page-ancestor before. wordpress uses li.current_page_ancestor
Remove ending div markers

Related to issue #486
Replace mixed spaces to tabs and make sure everything is indented correctly.
Merge pull request #508 from neojp/master

Replace mixed spaces to tabs and make sure everything is indented correcly.
Merge pull request #499 from elron/patch-20

Fix header nav style
Merge pull request #501 from Silex/master

Remove ending div markers
Minor Inconsitency
Merge pull request #515 from blowsie/patch-6

Minor Inconsitency
Merge pull request #500 from elron/patch-21

fix classname li.current_page_ancestor
Merge pull request #491 from bgallagh3r/master

Fix accessibility issue in the menu and cleaned up some CSS.
Merge pull request #415 from gthapar/patch-1

Update _768up.less