Interlinking within the site, setting up titles of your web pages, meta descriptions, maintaining content and etc are called on-site SEO, and getting links to your website from other websites is called off-site SEO. As mentioned earlier, content quality was very important and was highly valued in the world of marketing but the latest Panda update filtered out and put many websites that has very low or copied content into garbabge. Those sites were given penalty even by Google, i.e : Google removed such sites from its ranking and Google decided not to rank such sites anymore. As a result, blogs that copied the content from other websites and made a remake of their own content are affected to a great extent. So, these days content become more crucial, on the other hand, Google always emphasize natural link building, and the last panda updates focused on anchor text in backlinks as well.
You need to make sure to moderate the ads on website. Websites that have been created in specific to promote ads have been affected the most. Back links have always been the main reason for the success of a website. You must ask your London SEO consultant to pay attention on these details.
Source : http://seoconsultantslondon.webs.com/