I'm getting this error message "ERROR: Patch can't be applied/reverted successfully" when installing the SUPEE-10266 patch on CE 184.108.40.206.
Do i need to install some other patch previously?
How do I know which previous patches needed to install a new patch?
Normally you'll find some link with information in the download area.
For example: https://magento.com/tech-resources/download#download2073
You can access to this page from tat section: https://magento.com/security/patches/supee-10266
If all that information isn't enough, maybe you can use this tool from a member of the community: http://fabrizioballiano.net/magento-patches/