If you are trying to boot on unsupported hardware (like a 2006 Mac mini or a non-Intel PC without Hackintosh patches), the ISO will never work.
Once downloaded, you will see Install OS X El Capitan.app in your Applications folder. Do not run it directly. mac os x el capitan 1011 6 iso download gratis work
Any website offering a pre-made “Mac OS X El Capitan 10.11.6 ISO” is almost certainly a modified, third-party creation. These carry enormous risks: If you are trying to boot on unsupported