General case like this, there are some links to your blog which may now be on the first page of google search but did not appear a few weeks later-appear again on the first page of google,
If matters such as the above, cause there are some possibilities:
1. Blog you get google dance (dance with google .... finally gigoyang-shake and lost ...) Google dance is a term commonly used by the webmasters to define the behavior that is inconsistent google, this is caused by as many keyword typed by users of search engines within a very close, so google headache (hangover) and finally only can dance the dance of strike blogs google will get knocked out of position even 1000 large 100 SERP. The second possibility is the presence of synchronization some google server (usually a blog has the visitor is not from one country but some countries) after 3 months will be synchronized so that after 3 months the position will be normal again.
2. Possible lack of backlinks to your blog, your solution should increase both the quantity and quality backlinks. We recommend that you add links from other blogs that his homework is higher than your blog. or submit to social bookmarking, link exchange, etc.
3. The possibility of reduced traffic trends (patterns / traffic growth declined), you should try to get traffic to your blog
4. Possibility exists that you copy and paste your blog posts, to avoid effects that are too big you should take advantage of the blog posting dummy to create a similar theme (not the same as the original), then create a link from the blog posting dummy to the main blog (note: this way only personal opinion, may not be effective), or can also perform periodic secra editing posts.
5. Another solution, Create posts with the same theme on the same blog for further strengthening of those keywords in your blog.
6. Make a link (anchor text) that lead to your post, put the link in the menu bar or on the side bar or in a place that is easy to click by visitors (recommended in the menu bar / menu navigation for easier detection by the robot in google).
6. For a while points above that I can describe, hopefully a little help of friends who are beginners in the field of SEO optimization
Please try the SEO tips above hopefully useful.