The cynic in me sees two differences:
1) Much smaller user base
2) The Litmus ad on the right side of every page
EDIT: The rest of me sees healthy competition and an interesting take on freemium marketing for their money-making app. :)
1) Much smaller user base
2) The Litmus ad on the right side of every page
EDIT: The rest of me sees healthy competition and an interesting take on freemium marketing for their money-making app. :)
Also a much more focused user base. From an advertising point of view, do you think it's easier to sell 10,000 uniques on a general web technology site or 5,000 uniques on a site that has a very specific audience like web designers?
I can see them sharing the same database for both sites but displaying the CSS/HTML questions both on doctype and SO, but doctype restricted to CSS/HTML only. This will allow them to get content through multiple channels but allow them to sell more targeted ads on doctype.
With a much smaller subset of potential users I think you'll also find a much more "focused" group of advertisers, i.e. a smaller group of interested advertisers.
Since SO content is licensed under creative commons, there's no reason they can't feed in all questions into SO... I suppose it might be tricky to merge votes of the (much larger) SO audience with votes of their audience, and has interesting implications to SO's business, but it's certainly doable.