Zen Cart by default provides a successful install message on the index page. It goes:
Congratulations! You have successfully installed your Zen Cart™ E-Commerce Solution?
To get rid of it you need to FTP to your server and download the index.php file located at:
Make a backup copy of the file.
Open the file in a text editor and find the section:
// This section deals with the "home" page at the top level with no options/products selected
/*Replace this text with the headline you would like for your shop.
For example: 'Welcome to My SHOP!'*/
define('HEADING_TITLE', 'Congratulations! You have successfully installed your
Zen Cart™ E-Commerce Solution.');
Delete the 'Congratulations... ' and add your own text if you wish.
Upload by FTP the modified file and overwrite the existing.