A "good writing" content filter

A "good writing" content filter would help a content writer determine if his writing is good enough. 

He spotted that top-ranking web pages in Google are far better written than most. Their keyword density, link text, and PageRank were of little importance. 

Joe's results were taken from Google’s top five pages for the five most searched-for keywords. The body-text of these pages had the following in common:

Microsoft Word can check for errors in grammar and style, as well as check spelling. But it sometimes goes too far. For instance, it criticises the use of sentence fragments, which are a popular stylistic convention. Google appears to accept sentence fragments without penalty. Phew!

Other factors found to be important, from Joe's research, were:

Without doubt, Joe has identified some important factors here. They should interest anyone who has gone through the usual motions to get their page in the top five, and failed.