Reasons to your seo ranking fall down
Iactivity
If you're only updating your blog once every other week, you're unlikely to rank very high in Google, which generally offers higher search rankings to new content. Having new content gives you more opportunities to connect with readers and fellow bloggers as well; every time you update your blog, you also have a chance to update your Twitter stream, Facebook page and any other profile linked to your blog or blogging persona. Also, the more quality content on your blog, the more ways people have to find your blog via search engine.
Changes to Google
Google occasionally makes changes to how they index and rank websites and blogs; when these changes are made, some blogs often suffer a loss in page views. Darren Rowse of ProBlogger discusses a change to Google's algorithm in 2004 that cut his traffic by 2/3. His advice is to wait, give Google time to re-index websites, and take the time to make minor tweaks to the SEO, design and philosophy of your blog. He also recommends against making major changes in a panic; major and frequent changes may hurt your blog in the long run.
Changed URL
If you're recently changed your URL or your blog name, you may notice your hits have dropped, especially if the change in your website results in broken links all over the Internet. This can be less of an issue if you were previously using the free username.blogspot.com URL, as Blogger automatically redirects users and URLs to your custom domain. Changing between custom domains can be a bit more problematic. Changing your URL can break RSS feed links, losing you subscribers who may not even realize the RSS feed is broken.
Blacklisting
Your websites can be blocked from Google search results if you're found guilty of "bad" SEO practices. This includes stuffing your content so full of keywords and phrases that it's not comprehensible, using HTML or CSS to hide keywords on your webpage, stealing content from other websites and creating multiple blogs with the same content using different keywords. If your page is blacklisted from Google, there's really not much you can do to raise your rankings again, other than starting fresh.
Recovery: Increasing Traffic
First, continue updating your blog, even though the traffic is falling. However, try new things. Don't be afraid to diversify the topic of your blog; discuss topics that you find interesting in ways that are relevant to your readership. Test some new SEO methods, and don't be afraid to network with other bloggers in your topic. Twitter, Facebook and even link exchanges can all generate new traffic to your blog. Consider updating your blog to something a bit more modern and SEO-friendly. If your budget allows you, you might even consider buying ad space on another website.