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The new Marketplaces are available in Bulgaria, Costa Rica, Croatia, Estonia, Iceland, Latvia, Lithuania, Romania, Slovakia, Slovenia, Turkey, Ukraine, Venezuela, UAE, Bahrain, Iraq, Saudi Arabia, Qatar, Kazakhstan, Israel, Thailand and Vietnam.
The web Marketplaces are an alternative to finding and installing an app on your phone. You can find detailed instructions on how they work here.
Microsoft also announced it is working to improve the search on the Windows Marketplace by reviewing the keywords developers assign to their apps, and removing ones that aren't relevant.