We often come across a variety of clients who have used other SEO services from other providers or tried to attempt to do it themselves. Eventually they reach a point where their rankings disappear. This occurs usually when an seo provider has bought/made low quality spammy links. These bring more harm than good but can often yield short term gains. Another cause for the drop in rankings is that other competitors have copied your text and slightly altered it. This duplicate content may cause a drop in your rankings and a boost for your competitors. The first step to removing any poor spammy links is to use : http://linkquidator.com/
They offer a free 1000 link removal which in most cases is adequate for most sites unless there has been a huge amount of spam directed to your site. By logging into you google webmasters, it becomes visible if you have been hit by a penalty or not.
A common cause for a loss of rankings, is that your competitors have stepped up their SEO game and you have remained stagnant as time has passed. If this is the case then bring some new original content to your site and start back your backlinking. Ensure you have correct on page seo, as this is very often overlooked. If your still struggling with your site, the team at Code SEO is happy to create a competitor analysis and aid your website to recoup any lost rankings.
Another potential cause is a competitor has decided to play a dirty game of Negative SEO. This is very much a real practice and we would not like to describe in detail how this can be achieved however we would like to aid any business who has been hit by this dirty practice at a very nominal fee as we do not condone this behaviour and feel it is damaging the internet. Rather than competitors playing dirty they should focus on creating high quality links to their own site.