Know two things.
First, a symbol in bash may not contain colons, slashes, or periods. Period. I recommend you change them all to underscores, or get rid of them altogether.
Second, bash can get confused if you do something like
no matter what the current value of $SYMBOL is. You can get around that by using the "set" command (or the "export" command if you wish this symbol to be accessible by programs you run after that).
I recommend you play with something like this:
NEWSITE=$(echo $SITE | sed -e 's/[^A-Za-z0-9]/_/g' -e 's/$/DOWN/')
Hope this helps.