In addition to the regular Yahoo algorithm updates, time to time, Yahoo Japan has its own algorithm changes, which are unique to Japanese market. In December 2009, they had another major updates, and many experienced the changes in ranking. Here is a list of some of the changes I’ve seen in the past month.

• The authority pages are valued more
• The hub pages are valued more
• The accessibility and the file size are valued more

Of course, the competition level is different depending on the keyword, and that also determines how much of the changes you saw since the last update.

Now, in order to benefit from this update, I recommend following optimization work:

Check your inbound link landscape for numbers, IPs, and domains. This should give you an idea for the next step of your link building to make your site more authoritative website.

Create a chart showing how the web pages on your site are linked each other. This should give you additional data for the next step of your on-site link building and to make each of your SEO target page more of the hub page.

Lighten the file size and fasten the download speed. Remember, a page downloads quickly in US could take much longer to download in overseas.