I tried this solution
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]
as in https://stackoverflow.com/a/22299685 to redirect from non-www to www, it works when I tried it on my PC, also I checked the server header and it works fine (301), but when I tried on my mobile phone (android Gingerbread) using Firefox and type in example.com
but the result still example.com
not www.example.com
this should be not an issue since this is a Server Header.
I'm not using mobile redirect on the website, desktop version for every device. I typed in the code correctly.
RewriteEngine on
RewriteBase /
RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]
What I missed?
EDIT: Shoud I use a "mobile version" .htaccess that I didn't know? Any advice would be great.