Stake checks the code when you open it and will tell you if it has already been claimed or isn't available on your account. If Stake.com won't load, any online mirror below works too.
A mirror is a replica of an already existing site, used to reduce network traffic or improve the availability of the original site. The mirrors listed are direct copies of Stake.com and were made available via different URLs to assist players who are having issues connecting to Stake.