2.2. Reserved Characters
reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" | "$" | ","
2.3. Unreserved Characters
unreserved = alphanum | mark
mark = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"
excerpts from RFC 2396: Uniform Resource Identifiers (URI): Generic Syntax