If it is a golden brown and just a film it is likely diatoms. They almost always appear after a new tank setup and feed on silica which is in high concentration in new tanks and if you were to do a 100% water change or close to it.
However if they are a darker brown or even have a reddish tint with what may look like strings or filaments comming from it. Also it will form in mats on the sand and rocks, then you have "Red Slime Algae" or Cyanobacteria.
http://saltaquarium.about.com/cs/microalgae/a/aa092800.htmTo clear this up you need more water flow in the area where it is growing, and should cut back on feedings and possibly look into a better skimmer if you still can't get rid of it.
Rick