In order to get rid of annoying Microsoft Ads in Skype add these lines at the end of the file C:\Windows\System32\drivers\etc\hosts
UPDATE:
127.0.0.1 apps.skype.com
# Skype Ads Blocker
127.0.0.1 rad.msn.com
127.0.0.1 live.rads.msn.com
127.0.0.1 ads1.msn.com
127.0.0.1 static.2mdn.net
127.0.0.1 g.msn.com
127.0.0.1 a.ads2.msads.net
127.0.0.1 b.ads2.msads.net
127.0.0.1 ac3.msn.com
# End Skype Ads Blocker