Yahoo is one of the best search engines after Google, so it is very important to ensure that Yahoo is giving your site a good rank, because a site that is well optimized for Yahoo will also rank well in other search engines.
There are a few differences between Yahoo and other search engines such as Google. It looks that Yahoo places more value on number of back links than the content from the page, so, an established site with a lot of incoming links, getting a good ranking on Yahoo can come naturally.

Yes it is ok, but Google is much better than others search engine.

Thank you,
Regards,
Pakistan Boy