Desktop folders and applications disappear

Desktop folders and applications disappear
I was using my computer yesterday, for surfing the Internet. I encountered errors and pop-ups. I just closed them all, using right click on the task tray, then clicking the close button. After closing them all, I have shutdown my computer. I have noticed today after opening my computer, that all applications and folders in my desktop are all gone. What happened?
How can I restore them all, I have important files saved on desktop. Please help.
