Also, it is better to have a balanced set of 1's and 0's. It's not really useful to have a huge list of 0's, when there are only a few 1's (as the classifier only takes as many 0's as there are 1's to have a 50/50 set). So it's probably better to look for pages that are likely to list cohort companies and look at those first.
If you want examples of pages with and without cohort lists, you can look at some of the already classified examples, though there might be a few mistakes.