Dark matter probably doesn't exist. It is the theoretical result of calculations based on a wrong premise, i.e. that gravity alone governs the motion of galaxies. If you take account of electromagnetic forces too (the forces that result from electric charge separation in plasma), then there's no need to invent some exotic form of matter.
(see www.plasmacosmology.net)
Dark energy probably doesn't exist either. This is another theoretical non-entity that supposedly fuels the expansion of the universe. The universe probably isn't expanding at all though. The idea that it does comes from the assumption that galactic redshifts are a doppler effect when it is quite possible that they are instead a scattering effect. Light may simply be losing energy to matter in the intergalactic medium. (watch this:
http://bit.ly/sv3MGo)
The cosmic microwave background is probably the blackbody radiation emitted by matter in interstellar space. Basically space is full of matter but scientists didnt realise this when the archaic big bang theory was dreamt up. They treated it like a complete vacuum, and since then scientists have invested so much time and energy into the big bang thoery they cant bare to drop it now, so they desperately tweak their tired old theories which involves dreaming up new forms of matter and energy and making the universe out to be more complicated than it really is.
Here's a page that sums up the many flaws of the big bang theory:
http://www.metaresear...smology/BB-top-30.asp
Imo, the universe is eternal and static and really quite simple.