This is a knowledge base for your site. (Keep any usernames and passwords in your password saver, like 1Password.com, not here)
You must have all of these details about your website, even if (especially if) you have someone else helping with your site.
Website Designers and Developers
4 Steps for Saving Money on Your Website Development
Presenting Yourself Professionally on Your Artist Website with Jessica Burko (ep. 174)