Yahoo has rolled out new audience targeting capabilities that can help you reach more of the audience you want at the right time, right place…and at the right cost for you. The new demographic targeting, ad scheduling (dayparting), and enhanced ZIP code-level geo-targeting allow you to segment and tailor marketing messages to the audiences that are most valuable to you.

What's Changed
These are the new and enhanced targeting methods you can use, with comments from Advantage Internet Marketing:

Demographic targeting: This could be very valuable, although one should bear in mind that the demographic information is self-published by the user, so it is limited to users who have chosen to reveal their demographic details, and are searching while logged in. You can now select your desired audiences on Yahoo! sites—in both Sponsored Search and Content Match—by age and gender, and automatically adjust your bids when we find a match for your targeting preferences. With demographic targeting, you can take advantage of Yahoo!'s wide user base and our deep understanding of our audience. Demographic targeting uses a new feature bid adjustments, which lets you specify a premium bid amount for desired audience segments, without losing other traffic volume.

Ad scheduling (dayparting): This is a feature that Google AdWords has offered for some time, and Yahoo is only now adding on. If the people you most want to reach are only online at certain times of the day, or your business is only open during certain hours, you can select the time of day and day of the week during which you'd like your campaigns to run. You can schedule ads to be shown according to users' time zones or your account's time zone. Ad scheduling can be applied to both Sponsored Search and Content Match, and at the campaign or ad group level. 

ZIP code-level geo-targeting: An update to the existing ZIP code-level targeting feature, advertisers now have even more control about how geo-targeting is used. You can mix and match geo-targeting settings at different levels within the same campaign or ad group, and new dynamic mapping features can help you select individual ZIP codes and ZIP codes surrounding them. Once again, dynamic mapping is similar to an existing Google AdWords feature.
Summary: In general, Google AdWords is still the go-to online advertising provider. They have the lion's share of traffic, and the features you need to target your market. We recommend Yahoo only if you have sufficient budget to exhaust the Google traffic, or if there is a particular market served specifically by Yahoo.