Just to make it perfectly clear, there are two issues involved here.
1) The "/" conflicts with sed's traditional 's' command separator. Solution: use another separator. sed can use any basic ascii character, so just choose one that's not found in the string. Good ones to use are often ^, #, @, _, and |.
You could also simply backslash escape it if you wanted, but that tends to be less readable.
2) "." is the regular expressions operator for matching "any single character". So "/." in your expression would also match, for example, "/A". Solution: either backslash escape the dot, or confine it within a regex bracket expression "[.]".