Whenever a maintenance activity is scheduled, we use to publish message in the sign on page to intimate the users rather than sending mails. I remember every time an activity is scheduled, the login page HTML file (signin.html) residing in web server needs to be edited, which requires a minimal knowledge of HTML scripting. Moreover web server bounce is required to get the changes reflected in front end.
Guys using People tools 8.51 and later don’t need to worry about this, as there is a new feature with tools release 8.51 onwards where we have an option to configure display message via PIA itself and it does not require any code changes. In a single stretch you can create list of messages and you can set the time frame to display that specific message.
Navigate to People Tools > Utilities > Administration > Shutdown Msg (PT 8.53),
Click on the plus button to create new message and View/Edit hyper link to edit the existing message.
Once you click the plus button, you will find a space to post your message and also you can find an option to specify when and how long the message should be displayed.
I have replicated this post @ http://www.citagus.com/citagus/blog/custom-message-setup-on-peoplesoft-signon-page/