If you have ever had your web site near the top of the rankings for relevant search terms it can be a very heady experience. This is especially true if you are able to capture the #1 ranking for a search term related to your product or service.
1. Your competition is getting more and better inbound links to their site.
2. Some of the in-bound links to your web site have been devalued.
3.A search term you once had good ranking for is now a term that Google has determined requires freshness and information sites are replacing the product related or commercial sites for that term.
What remedies do you have? First and most important, make sure you continually build inbound links using search related anchor text to your site. You can find out which sites are linking to your competitors and get them to link back to you. You can also create your own linking strategies. These strategies can include consistently creating new content. Techniques include article writing, press releases, social networking, integrating a Word Press or Blogger.com blog into your root domain and disseminating you own RSS feed. You can also do one-way linking and reciprocal linking with theme related sites if you are in a small niche.