These days you can find lots of SEO software that provide onsite seo tips, but it seems they are different from one product to another.
I want to implement my own tool for checking page optimization, but I need some proven onsite checklist (maybe published by some authority site) to use as a guide.
For example, is it written somewhere that titles should exceed 80 characters in length ? Is there a lower limit for titles ?
What about length of the H1 tag ? ... you got my point.

Thank you