Using a different salt for each user presents an issue: the salt isn't known until the user name is known. For a web application, this would require a two-stage login form - one form asking for the user name and a second asking for the password. Such an arrangement would be quite unfriendly towards users. Fortunately, there is a simple alternative. The salt is generated by concatonating the user name with a "system salt". The system salt is the same for all users on one system.
Regarding the salt, the page says:
Using a different salt for each user presents an issue: the salt isn't known until the user name is known. For a web application, this would require a two-stage login form - one form asking for the user name and a second asking for the password. Such an arrangement would be quite unfriendly towards users. Fortunately, there is a simple alternative. The salt is generated by concatonating the user name with a "system salt". The system salt is the same for all users on one system.