Search results on Yahoo now include the HTML lang attribute which has important consequences for screen readers:

If you do not see the text but you get it read out to you then the pronounciation is very important. Visually impaired surfers use screen readers to tell them what is on the current page, and by defining the language, you make this a lot easier. Screen readers have different voices for different languages with the correct pronounciation rules.

Yahoo! search results now with natural language support