Wallbase.cc doesn’t exist anymore. The owner of the website, “Yotoon” (nickname) was responsable with the website.
Considering the official Twitter page: https://twitter.com/Wallbase, Yotoon hasn’t showed any sign of life in the past year. The website was online but without any updates/uploads.
The team around Wallbase has come up with a new website that is using pretty much the same script/design as wallbase.cc. It will be called wallhaven.cc.
You can find the alpha version here: http://alpha.wallhaven.cc/.
They said that all the wallpapers from the old wallbase.cc will be uploaded on the new website when this one will go beta.