All the low profile and low domain authority backlink are down your site try to put a link on high profile domain authority sites ,your niche related sites this will helpful to improve your site...
If you came across with this drop in ranking, than it might be because of the recent unconfirmed Google update, Fred on March 9. Many website came across with the drop in ranking and traffic after this update.
Social Bookmarking - 100 digs for some pages
Example: I had a Web 2.0 Design Tutorial website and got about 100 digs for some articles, technorati, del.icio.us and so on.
When checking backlinks digg.com showed only 5 of them.
Conclusion - Pretty good but make sure your article is 110% original.
You may be implementing Black Hat SEO techniques which is making your website rank to drop. Avoid keyword stuffing, duplicate content, cloaking, hidden text or urls etc.
or you may be using
1. Stop building low quality backlinks.
2. Avoid Low quality blog directories