As of Monday morning, Wikipedia is either not available at all, or opens with obvious difficulty and with a broken make-up.
On the wikimedia foundation twitter it is reported that site engineers are busy fixing "some technical issues."

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The status of the resource can be seen at this link -
status.wikimedia.orgSo far, like this (18:00 Moscow time)
viaUPD At 20 00 (Moscow time) is working normally.
The source of the problem was the sudden disconnection in the data center (Tampa).