Apache asks the password for each subdomain with htpasswd.
I want that he would ask the password at the first input and remembered me for all subdomains
I use the following code:
AuthType Basic
AuthName "Projects"
AuthUserFile /blablabla/baz.htpasswd
Require valid-user
Actually Apache httpd asks for your user credentials on every request on every subdomain. It's your web browser, which caches your credentials (per hostname) and sends them on every subsequent request on the same hostname.
You can't really circumvent that behaviour without full control over your clients' software if you want to keep the different subdomains.