I am receiving job proposals in Stack Overflow time to time. I currently have a good enough job and not willing to change it, so I need to reject these proposals. However as we all know life is long and nobody knows. Maybe a meteorite will hit my office building tomorrow, destroying it to ashes. Or something that is more probable and happens more often. Nobody can be sure.
What is the best way to say "no" such that I would be able to apply for a position in that company later? I also may not reply, but this is a kind of response as well. There is a button "I am not interested in" available to me, but I am not sure if hitting it would not be a rather rude way to respond.
This is the specific focused question: Stack Overflow job message board, but is not technical because I am asking for the message that human will read and make a decision about me.