Skype is an instant messaging service that you can use to keep in touch with friends and family. Your contacts window can show you who is online and who is offline. If you want to free up some space in your contacts window, you can choose to hide contacts who don't meet certain criteria. For example, you can hide contacts who aren't online or contacts who haven't shared their contact details with you. Unhiding Skype contacts takes a couple of mouse clicks.
Sign in to Skype, and then click "Contacts."
Click "Hide Contacts Who."
Click on an option to uncheck it. For example, if you have offline contacts hidden but want to show them, click "Are Offline." To show all of your hidden contacts, make sure there are no ticks left on any option.
If you have more than one Skype account, make sure you are in the right account to see the contacts; they made not be hidden -- they just may be listed on your other account.