The web-site has ssl certificate.
Any http page is redirected to the same, but https page (if not https) by .htaccess.
Everything works fine, but 404.shtml gets a security warning “This webpage contains content that will not be delivered using a secure HTTPS connection…” in IE. The same behavior is in any other browser.
How to exclude that error?
404.shtml web-page was created using web-hosting control panel wizard. The file 404.shtml was created automatically.
Most likely the automatically generated file includes links, images or other resources fetched via http. If you can change them to https links, you should avoid the problem. There’s afaik no other way to make the browser not warn about this, at least in a cross browser way.