Is it proper for a civilian to salute a member of our Armed Forces?

I saw a group of servicemen today getting ready for a local parade. As I was driving by in my work vehicle, I tapped the horn and gave them the crispest salute I could muster. I haven't had the chance to serve (closest I get to ANYTHING military is the Cub Scouts maaaany moons ago), I just want to know if it's a proper way to show our service men and women they have my support. I don't expect a salute in return because I know it doesn't work that way, it's me showing the pride and respect I have for THEM.