For checking certificate or declaration you should visit the site Rosaccreditazya by link http://fsa.gov.ru/, and then go to the section "Реестры".
Federal Service for accreditation has 10 registers, but for finding the needed document you should select from the list:
In the window that appears is necessary to fill suggested menu (one or more, depending on the information that you have) and click "Поиск" (Search).
Then in the opened window you will find only the needed document and information contained in the register when registering.