I\'m using the fragment identifier to create a permalink for AJAX events in my web app similar to this guy. Something like:
http://www.myapp.com/calendar#fi
http://tools.ietf.org/html/rfc3986#section-3.5:
fragment = *( pchar / "/" / "?" )
and
pchar = unreserved / pct-encoded / sub-delims / ":" / "@"
unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
/ "*" / "+" / "," / ";" / "="
pct-encoded = "%" HEXDIG HEXDIG
So, combined, the fragment cannot contain #, a raw %, ^, [, ], {, }, \, ", < and > according to the RFC.