You will need to set up Docdata with details of where to send updates on the status of payments to, and whether to redirect the user to after payment. To do this, login to your Docdata account, then go to Settings > View/Edit Merchant Profile, then click the URL button near the top. You should see a form like this:

The Update URL is the most important setting; this should point to the callback.aspx page on your site, for example:

http://www.mysite.xyz/callback.aspx?g=docdata&mt_id=

It's important that you leave the mt_id= at the end; Docdata will append the order ID number to this. This URL is not called in a user's browser, rather it is called directly by Docdata each time the order status is updated.

The other settings control where a user is sent immediately after payment. We suggest you create custom pages in Kartris for each, so you can design the message to show to customers. For example create pages called:

Success
Cancelled
Error
Pending

These will have the URLs as follows:

http://www.mysite.xyz/t-Success.aspx
http://www.mysite.xyz/t-Cancelled.aspx
http://www.mysite.xyz/t-Error.aspx
http://www.mysite.xyz/t-Pending.aspx