Webmaster tools shows that I have about 125 "urls not found" and that the detection of these has been slowly, buy steadily, increasing. A lot of this is old urls that existed before I foolishly changed the site structure without knowing what I was doing. In fact, I'm pretty sure I've done that twice since I first created the site two years ago. I simply deleted pages without redirecting to new urls. Other "not founds" are external links that I can maybe can get deleted.
As there's no other indication in webmaster tools that there's a problem with my site, I'm assuming that the accumulating "not founds" are the problem. I never did any serious backlinking (only used BMR for a couple of months) and have reduced some of the internal linking within the site, keywords, and changed some of the anchor text. I never engaged in any kind of link buying except for the brief time I tried BRM, and even then I didn't do very much.
I've added a few new (and good) pages of content, and have been waiting to see if anything would change in my rankings, but no, nothing.
I've thought of simply creating a new site with a similar domain and use the same content but don't want to redirect all the problems with old site to a new one.
However, I would really like to put the content to good use. Is there any way I can just take the old content and use it on a new domain without it looking like copied material?
If I added a lot more new pages so that I have as many new pages as old ones, would that help?
If anyone has any advice I would love hearing it.