You may have difficulties connecting to your Minecraft server from time to time. Common error messages include Failed to login: Error or something with session.minecraft.net/..., or an error code of 503. The errors typically indicate something wrong with the minecraft.net login servers, which authenticate the player names with registered Minecraft accounts. It is not a problem with our service. You’ll be able to connect as soon as Mojang fixes the login servers.
The best way to keep track of Minecraft service uptime is to check out this mcstatus tool or the official Minecraft status Twitter account. We’ll usually post updates about such outages to our Facebook page and Twitter.
You can also check if others are experiencing the same issue by searching on Twitter. Search terms provided are minecraft.net down.