Really sorry about the downtime.
It appears the server went down on Monday, and unfortunately I was unaware of it until Thursday when I fixed it. This typically wouldn't be a problem as I usually check on the site every day, but I was away for some of this week and apparently that's right when the server thought it best to become unavailable. To prevent this from happening again, I set up a notification system which will automatically check on the site a few times a day and email me if there's an issue.
Everything should be restored now, but unfortunately four days of stat gains (May 7 - May 10) are not available due to the downtime. If you look at your User Progress page, you'll just see the same rank/xp/level values repeat for those days, as no other data was available. However, from May 11 onwards, all xp gain values should return to normal.
I don't think there should be any further issues, but if you spot any area with any missing data, please post here or in Bugs and I'll correct it. As for the Recently Gained Levels chart, levels gained in the downtime period won't display (however this usually shouldn't be an issue because the chart is always showing the most recent level gains, and eventually those that didn't appear would be pushed off anyway).