I was able to normally access my files last night, but today they're gone.

Thanks for letting us know about this, Russ147. Let’s have a look.

To clarify, you were accessing your Dropbox account via www.dropbox.com both yesterday and today, but your files were visible on your web account last night, correct?

Have you checked your Events page here? If yes, do you see any events that would explain why your files don’t appear in your Dropbox account now? 

Please also make sure to have a look at your Deleted files page, in case any of your files have been accidentally deleted, and your Shared tab, as well.

Let me know what you find.