@Dariusz,
I'd recommend going to the runbots:
runbot.odoo.com
and logging into an 8.0 instance. Just go back to the contact us page once you've logged in (login: admin passwd: admin). You should just be able to go where you where before and copy paste the original back in place.
For editing using the HTML editor, please note you are using a mixture of XHTML, and QWeb markup.
For any customisations if you are on a localling installed instance rather than an Odoo.com hosted instance i'd recommend building a simple module that inherits the view and changes the parts you would like to change. Using this method it is much easier to roll-back changes, you simply uninstall your simple custom module that has applied the changes to that view.
@Dariusz "website" module try to upgrate default contactus template ID Created in Website module and "website_crm" module contactus inherited.
I updated my answer