If some one tells you you're hot but they don't know you, what do you do?
For example, if you have a disability and you really like this person, do you tell them and risk stopping the acquaitance or tell them later when it might seem like you lied to them?
First and foremost, when someone pays a person a compliment, the correct thing to do is to accept it graciously. Never call the person who has paid the compliment's taste into question by denying their claim. In other words, do not say, "No, I'm not," or something like that. Just say, "yYou are very kind/sweet/considerate/etc. to say so." This way, you neither acknowledge that the statement is true nor do you call the person a liar, you just confirm that the person was kind by making the statement.
As far as the requirements for full disclosure go, it varies from person to person. In my humble opinion, honesty is the best policy. That being said, however, there is a time and a place and some truths may never actually need to come out at all.
There are some basic truths, the withholding of which will be considered the same as lying. For example, if you are a man and the person you are chatting with obviously thinks you are a woman; if you are a woman and the person thinks you are a man; if there is a significant difference in your ages, and the place online where you contacted the person first is age specific. (e.g., if a middle-aged man contacts a girl in a teen chat room and doesn't reveal his true age, it would be wrong.)
As far as physical characteristics go, it gets a lot muddier. Again, if you contacted the other person in a specific type of room that your physical characteristics don't fit, then that person could think you lied to them with some justification.
However, if you met in a general place where the other person has no expectation of any specific truth, and that person furthermore does not ask you about whatever disability you are worried they won't accept, then you are not under any moral obligation to reveal it.
Until, of course, you sense that the relationship may be getting serious. I would say, though, that "You're hot" does not constitute a relationship moving into a serious state. Wait until the talk moves to marriage or at least meeting for the first time to worry about revelations.