Error establishing database connection?

I was adding a new user today,
theme uploaded bloat and i was deleting it through the posts, pages, categories

while i was waiting on it to return so screen so i could delete more bloat to trash i got this error...
Error establishing a database connection
If your site does not display, please contact the owner of this network. If you are the owner of this network please check that MySQL is running properly and all tables are error free.

Database tables are missing. This means that MySQL is not running, WordPress was not installed properly, or someone deleted wp_cyyu_site. You really should look at your database now.

What do I do now? Read the bug report page. Some of the guidelines there may help you figure out what went wrong. If you’re still stuck with this message, then check that your database contains the following tables: