Improve HTML style CSS

[pbiering]

I received recommendations to improve the HTML style

I've applied them here:
http://mirrors.deepspace6.net/howtos/Linux+IPv6-HOWTO/index.html
(multipage)

http://mirrors.deepspace6.net/howtos/Linux+IPv6-HOWTO.html
(singlepage)

Please check whether this is useful also for documents publised on tLDP

[AliMD]

any plan to update your styles?!

[ser]

yeah, true, it would be fantastic to update them

[jordialcoister]

The documents need a new, cleaner face and the @pbiering proposal (thank you so much!) seems like a huge step to me... I might help with that, if needed...

[ser]

It would be fantastic if you could help, @jordialcoister !