Does light have Mass?

So the question "does light have mass?" Than becomes "what does it become in its next structure transformation? "

Depends on what part of ray of light you are referring to. Photons? What about that heat, you feel on your face, from sunshine? What form does it take next? Is it in the luminous category?

Luminous would be the 5% of the Universe that we can observe. Dark would be the part we know is there. But we can't observe it because it is either too dense and the gravity absorbs reflective material, or it is not dense enough and the reflective material flows through it.

Is there evidence against it?

So it stands until it can be proven different?

Well we know that the dark energy sector of the Universe is growing. So the volume can be measured. Find the source that it is feeding it, measure the rate it's volume decreases, and that will give us the numbers verify the formula.

When you release an electron from an element, it expands to a greater volume. But it never disappears. So when would the energy it released expand enough to enter the dark categories?

When an electron no longer has opposite forces, like protons near it, does some kind of decay occur? Or does it hold its structure infinitely?

We know how to measure units of energy from the formula
http://en.m.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence
So how many units of energy does a typical photon contain?

What is happening to these units after they are no longer photons?