Add missing queries_s4.html.

Signed-off-by: Daira Hopwood <daira@leastauthority.com>
how_it_works.html: need git as well as darcs, for now.

Signed-off-by: Daira Hopwood <daira@leastauthority.com>
howtoconfigure.html: recommend Tahoe-LAFS v1.10 instead of v1.9.2.

Signed-off-by: Daira Hopwood <daira@leastauthority.com>
If email is invalid, give another chance to sign up on the same page.

Signed-off-by: Daira Hopwood <daira@leastauthority.com>
Change address for reporting broken links to support@ .

Signed-off-by: Daira Hopwood <daira@leastauthority.com>
valid_email.html: one less exclamation mark.

Signed-off-by: Daira Hopwood <daira@leastauthority.com>