Is there any way to save a Facebook post as third-party evidence to use in the court room? I need an authentic way of saving it, where the judge and juries will not cast question on the saving procedure or the authenticity of the Facebook post.
To a broader sense, how can I save all types of web pages, whether they need log-in process or not, for court room use?
In the United States, it does not matter how you save any evidence; the other side will essentially always be permitted to question its authenticity. Even if they don't question it, a judge or jury would still be free to do so.
That said, the standard means of saving this kind of evidence would be to make a screengrab or print it to PDF, and to attach that to an affidavit in which you swear that the image is an authentic representation of the content of the web page as of whatever date and time.
If you want something that is harder to question, you could also ask some independent third party to do so. There are, for instance, archiving services like archive.org and perma.cc that will copy a page and store it indefinitely, largely removing the question of whether you might have manipulated the page in any way.
The basic way to save it is to take a screenshot. This has little actual probative value beyond your own credibility; it is trivial for someone with basic HTML skills to forge a Fakebook screenshot, but it at least creates a document that you can authenticate and submit. A more advanced technique would be to get some sort of verification by someone a finder of fact would consider to be trustworthy, such as a notary or police officer. Since Facebook uses HTTPS, the data constituting the post should have a digital signature, so if you can record that with the data, that should be strong evidence of the authenticity. Ultimately, if it remains in dispute, there is the option of subpoenaing Facebook, but that is unlikely to be used in minor disputes. Keep in mind that even if you were to subpoena Facebook, the opposing party could still dispute who made the post. At most it would show that someone with access to the account made the post.
