Currently, almost every Stack Exchange site has its own login area, meaning the browsers login auto fill doesn't always work.
Stack Overflow login:
Physics Stack Exchange login:
If I've saved my login credentials for Stack Overflow, they don't work for Physics Stack Exchange. I have to save them again, and vice-versa.
I propose a solution similar to that of Googles' is implemented,
accounts.stackexchange.com shared by all Stack Exchange sites.
Someone has flagged this as a duplicate of this, but I assure you, it is not. That post is about how sites behave after logging into one of the sites, and this post is about unifying the login experience across all the Stack Exchange sites, so browser login auto-fill only needs to remember one set of credentials for one address:
Here's a screenshot of my browsers password manager, ridiculous!!
All the credentials are the same.