In CMS Made Simple you can create your own customized "page not fond" and "forbidden" error pages.

Step 1

Open the Content Manager in Admin: Content >> Content Manager

Create a new page, by clicking on "Add new content"

Step 2

Change the Content Type to Error Page

Enter the title of the error page, for example "Error 404: Page not found."

Step 3

In the Options tab, choose the error type, and, if necessary, a design and template.

Step 4

Enter your custom content text and/or images.

Save your page by hitting "Submit" and the your customized error page is ready.