If you operate a Tumblr blog, you’re probably aware that the site experienced a major outage yesterday. After experiencing intermittent errors and slow loading times on a number of pages, Tumblr decided to take down the whole site “in order to resolve the network issue.”

That resulted in 4 hours of down time and a loss of nearly 100 million views to user blogs, according to the company. They’ve issued an apology this morning for the outage

Here’s the full Tumblr staff post:

Our engineering processes seriously failed this afternoon and cost you and your blogs nearly 4 hours of downtime and almost 100 million views.

Painfully, this isn’t the first time this winter I’ve had to give you similar news.

When incidents like this happen, our entire engineering team comes online to support the recovery as needed. Immediately after, we begin taking every measure to protect from the uncovered issue in the future.

We are constantly working to shore up our processes and solidify the stability of this quickly growing network, even more so as we’ve fallen behind the last few weeks.

Tumblr’s success is supporting your success, and we take this mission very seriously.

Tumblr was hit with a major outage back in October, too. And earlier this month, the site was plagued by a worm that ended up hijacking thousands of blogs.

Why issue an apology for a 4-hour outage you might ask? Apart from the fact that Tumblr often does this whenever there is a sustained problem, the site is one of the biggest in the U.S. Late last month they announced that based on Quantcast data, they were currently the 9th biggest site in the country. Globally, Tumblr has a monthly audience of 170 million people.