I just inherited a salesforce account from a previous owner, which is integrated with a number of custom forms and services. I'm not clear on all of the details to be honest, but I think this is a reasonably straight forward question.
I have a (custom?) field on leads called "Lead Source" with values like "conference," "website," "existing customer," etc. Occasionally I get a lead with this field populated by the value "Website":
The problem is that "Website" is not in the Picklist Values. Here is a screenshot of the picklist values, and you can see, it does not contain the value "Website":
To make matters even stranger, I can edit these leads and see a picklist with "Website" in the allowed values list:
So my question is, what could possibly be creating these leads? And, whatever is creating these leads, how is it able to assign a value which is not in the picklist?