Earlier today Skype had gone down for millions of users. Skype has now issued a statement on how and why this happened.
They explained that Skype relies on connections between millions of computers or phones. Some computers act as “Supernodes” which help locate the person that you are trying to connect to. For some reason today many users were taken offline because of a Skype version mismatch. So Skype engineers had to bring up many “mega-supernodes” to help counteract the downtime today. So if Skype isn’t up for you yet, it should be returning to normal shortly.