Layer with width/height 100%

Working with layers type container to set the values of height/widht 100% does not work. The width covers the entire screen, however the height covers only 80%.

I need a layer that covers the entire page to make a loading.

Problem solved. Carelessly left by the parameter "y" setted with a value (-). Assigns the value 0 and corrected.

In matter of performance is best to use a Layar (container) 100% height / width to create an effect of opacity or a plugin (image) 100% height / widht?