Have you ever clicked the update button for the plugins on your self hosted WordPress blog then refreshed the screen too early and got stuck on this screen?
It’s pretty scary to see, but there is an easy fix, and it’s as easy as deleting a file.
Log into your FTP account (the below screenshot is from Filezilla, but there are tons of other FTP programs available, including net2FTP which is based in your browser
See that .maintenance file? It’s a tiny file, but that’s what’s bringing up the maintenance screen. Delete only this file, and refresh your site. Voila! Your site should be performing as it should!
If this doesn’t work, then your next step should be to speak to your hosting company who should be more than happy to help (and if they’re not? Time to find a new hosting company!)