MicrostockGroup

I know you should separate all keywords with commas, but should you put phrases in quotation marks?

i.e. alley, alleyway, “back alley”, bin, bins, city, dirty, “run down”, dumpster, dumpsters, garbage, gutter, lane, polluted, road, street, urban, industrial, industry, construction

I've noticed some sites take them and some sites break up the quoted parts.  Is there one system that works for all sites?  Are the commas enough?