Hopefully this is an exhaustive list of things to check when your site will not scratch:
1) Is your site a spam blacklist? This is rare, but Facebook and most other tools will not analyze your site at all if it appears in the black list of spammers.
I am using https://admin.uribl.com/ as a check. If your site is listed, you need to find and clean the malware on your site, and then follow the instructions of the owner of the blacklist to delete your site. If the problem is that you have a host that is a known spammer, you will need to change the hosts. It will take several days for this to make its way through the system before any site cleans your site again.
2) Is your (X) HTML valid? The Facebook parser is very strict. If the headers sent by your web server or your HTML are invalid, Facebook will not analyze your site. To check this in detail, use the Markup Validator from W3C . You must resolve all errors before Facebook analyzes your page.
Some of the most common errors I've seen are the following:
- Invalid line sent in headers
- There is a mismatch between the
character-encoding sent in the header and the <meta charset> in the document. - Invalid or Invalid
<!DOCTYPE> - Spaces before the tag
- Formatted HTML tags, especially in
<head> - Tags closed with
> instead of /> in XHTML documents
3) Do you redirect your visitors using JavaScript? Facebook parser does not execute JavaScript. If you want to redirect the visitor to user-generated content, you need to do this from the server side of the script.
4) Does the server refuse to refuse connections with non-browsers? This is harder to diagnose, but some servers are configured to return 500:Server Error or 403:Forbidden for any non-browser visitor.
5) Does Facebook tell you your link is blocked? Log in to Facebook and try to share the link on your timeline. If your site appears in the Facebook internal blacklist, you will receive a message about blocking the site. There is a form in this dialog box in which you can mark this as a false positive and request a review of your site.
If you get on this list, Facebook users block your posts or mark them as spam. This probably comes from your content. What you think is SEO, probably spamdexing or the content you use is offensive or polarized to some users, or you just share the same stuff over and over again.
After fixing the error, go back to Facebook Debugger . A manual visit to the debugger clears the Facebook cache for this URL. Allow a few minutes for Facebook to update all servers, and then try again.