  We propose a design for an universal absorber, characterized by a resonance
frequency that can be tuned from visible to microwave frequencies independently
of the choice of the metal and the dielectrics involved. An almost resonant
perfect absorption up to 99.8 % is demonstrated at resonance for all
polarization states of light and for a very wide angular aperture. These
properties originate from a magnetic Fabry-Perot mode that is confined in a
dielectric spacer of $\lambda/100$ thickness by a metamaterial layer and a
mirror. An extraordinary large funneling through nano-slits explains how light
can be trapped in the structure. Simple scaling laws can be used as a recipe to
design ultra-thin perfect absorbers whatever the materials and the desired
resonance wavelength, making our design truly universal.
