I have a site that is almost 10 years old, pr5 and always been on page 1/2 for my main keyphrase ... (keyphase is 2 words <kw1> <kw2>) For a few months it has been jumping from the bottom of page1 and top of page2. A week later i was at the middle of page2 A week later i was bottom of page2 Now when i look my home page is NO WHERE to be seen? however, one of my other deep linked pages is now about the middle of page 2???? wtf .... this deeplinked page shares <kw2> with my home page but <kw1> no where on this page? I also have NEVER see this page anywhere near the top 100 serps for this keyphrase??? Any ideas whats going on with big google.
maybe some webmasters are interested to build site with same niche with yours. You should do better SEO technique to get back your ranking
You might be a victim too, just like many other sites who just exist there and been ranking for so long and just suffer like that, mostly because of recent changes in Google algorithm.
Your deeplinked page might show in search results even not having single word of the first keyphrase in its content unlike your homepage has. The reason, the deeplinked page might be a newly created content/page. Keywords ranks are not permanent. Since last two years and more precisely in the last year Google had taken few major steps to update its search algorithms. They are: Google Instant, Caffeine & Places. The total scenario of search results and algorithms had dramatically changed with these three major updates. However, I cannot judge the specific reason why your deeplinked page is ranking in the 2nd page of Google without knowing the keyphrase it is ranking for. So, tell me exactly which keyphrase you think the deeplinked page is given prior and not the Homepage + your homepage and deeplink URL's.