joomsef creates links like www.xxx.com/1.html, 2.html or 11-1.html, 2-2.html... Is there any way to prevent this?

Also, Google still finds 404 error on some pages which are not stored under "SEF URL" list. Why?

Hello,

These may be the pages in pagination on your home page, if you have a list of articles on the home page for example. You can disable the "Number duplicate URLs" option in JoomSEF's configuration and enable the "Handle pagination as non-SEF" option in Content JoomSEF extension parameters.

The URLs found by Google may not be processed by JoomSEF, that way the URLs are not stored in URLs Manager. Either the component generating them does not support SEF, or the Default Joomla router is used to handle those URLs.

Best regards,
ARTIO Support Team