This is populated by the cookie SignOnDefault. The cookie is set in the psp servlet and the value is passed back and forth between the cookie and the USERID session variable during the login process. The signin.html page uses JSP to populate the field with the value. An easy way to remove the UserID from the sign in page would be to take out the JSP. If you edit signin.html in the PORTAL.?war?/WEB-INF/psftdocs/<sitename> path and remove <%=USERID%> from the value of the form that will stop the population of the UserID on the page. In addition you may want to remove it from signintrace.html as well. Modifying this file would require a Weblogic restart and if you ever redeployed PIA for anything (upgrade or patch) you'd need to make the update again.