Re: letter limit on user names
“Size” is the display width of the field in characters.
“Maxlength” prevents you from typing in more than that many characters. The browser honors that and prevents more than that characters from being entered in the field. There are ways around this, but if you’re not in a hostile environment, and it’s all people from your organization, then lowering the maxlength just serves as a reminder to use a shorter name.