Just a quick post this week, on a little pet peeve of mine.
Folks, alter and altar are two different words. To alter something means to change it, to make it different in some way. "The main road was closed so we had to alter our course." Or, "I had to take the dress in to have it altered."
An altar is the table or other such structure where you preform religious rites, worship, leave offerings, etc. "I have a statue of Artemis on my altar." Or "I left offerings to the spirits at the altar."
Like I said, not the most earth shattering thing, but a mistake that's quite common.