Currently my site has around 5500+ pages indexed by Yahoo. But after 440 pages, yahoo started using "page URL" instead of "Page Tile" in indexed page title. I guess it does not help me with serp. Anyone has any idea why yahoo using page url? My site is data driven site and I am not using any mod_rewrite. Any idea?
It sounds like you have some pages that are dynamically generated, and that you do not have a page title defined (however you setup the page title w/in the system.)
What's your website, maybe as above said, your page is dynamic generated, and the original pages don't have a title, description, etc. Under such case you shall also generate dynamic title, description, etc for each page. Or you shall check your title, description submitted to yahoo directory and DMOZ, sometimes, yahoo will use these data to show your title and description.