3811564.fls.doubleclick.net is not a consumer website — it's a technical endpoint within Google's DoubleClick advertising network. If you encountered this domain in your browser's address bar or a network log, you're looking at Google's own infrastructure, not a third-party site. For an ad server, the security is excellent: a valid TLS certificate from Google Trust Services, no malware warnings, and a clean blacklist record. The subdomain itself currently returns a 404 error, which means it isn't actively serving content at the moment, but that doesn't indicate any problem.
Because this is a subdomain of doubleclick.net (owned by Google), questions like "is 3811564.fls.doubleclick.net a scam" or "is 3811564.fls.doubleclick.net fake" don't really apply. Google isn't a fly-by-night operation. The lack of an about page, contact info, or legal pages is completely normal here — those belong to the parent domain, where Google provides thorough privacy policies and terms.
If you're checking this domain because you saw it in your browser's developer tools or an ad blocker log, rest assured it's legitimate ad infrastructure. There's no hidden risk. The signals all point to a trusted part of the web's backbone, not something to worry about.