September’s Web traffic numbers are out, and — not surprisingly — online news sites fared impressively well. On average, the general news sites had a 32 percent boost in traffic. Despite being U.S.-only numbers, anecdotal evidence suggests Canadian sites (like CBC.ca and CANOE) experienced similar growth.

The big question is whether the news sites can sustain that level of traffic.

New initiatives from both MSNBC.com and CNN.com may help: the sites separately announced they’ll be offering Arabic language services (actually, GN4MSNBC.com launched today, and CNNArabic is launching soon.

News.com has an interesting piece on these latest Web traffic stats showing how pop-under ads can push a commercial site into the top 50.

Despite the fact this statistical fluke seems only to influence Media Metrix’ numbers, how can these numbers safely be used to sell advertising?