Splashmoop and Danielckx, if you read my post at viewtopic.php?f=1&t=10059
, you will discover that you are not the only ones who have experienced connection issues which clearly seem to stem from some conflict occurring between El Capitan and the latest Little Snitch nightly build.
In my case, it concerned connections to the App Store, as well as with my locally-hosted websites, which were offline for more than three weeks, until I found a temporary solution to the problem early this morning.
Everything was fine on my end up to and including El Capitan DP7. However, the minute that I updated to El Capitan DP8, the localhost/127.0.0.1 loopback was completely broken, and I, along with the rest of the world, could no longer connect to my websites.
In fact, localhost connections could not be made, regardless of whether I used Firefox, Safari or Google Chrome.
Furthermore, this El Capitan-Little Snitch conflict not only negatively affected the web server software which I currently use, but it blocked the localhost connection in another popular web server software as well.
It was only by disabling Little Snitch's network filter -- leaving me without protection -- that I was able to get my websites back up and running again, and could connect to the App Store easily again.