My site 665 pages since February ALL pages indexed but one, not one supplemental, not one url-only.
Before BD half the site (over 300 pages) turned url-only which as I read is one step before turning supplemental.
I initially thought it was a dup content issue as on many pages I had the same piece of text containing internal links. Then I reconsidered as I found many pages with very large original content getting url-only too.
Meaning I was mixed up and unable to understand the reason why the pages went url-only.
I took the decision to re-design each page – it took me over a month – didn’t particularly enjoy the X/mas holidays I must admit…
Here’s what I found while editing each page, one by one manually (I am not using templates, I write my own html):
1)Some of the pages did not contain ENOUGH original content – I removed the similar text and reduced the number of internal links.
2)Some pages with plenty of original content contained outbound links to banned or inexistent domains. Many of them contained articles by people whose sites no longer exist. I kept the content and deleted the link..
3)Some of these url-only pages had the same titles or descriptions by mistake – I corrected them of course.
4)Finally a few pages contained broken links (my mistake)
In examining around 100 sites in my industry I am noticing that there is NONE without at least a couple supplemental or url-only listings – I am the ONLY one with all pages crystal clear!
In closing, may I note that I had made a clean-up around 8 months ago so I thought everything should be OK, but no, seems like I must be checking on things constantly – it’s like housewives, cleaning your house today doesn’t mean it will still be clean next week -;)