One of the most annoying parts of Lighttpd is that it sometimes fails with error 417 when you upload a form or use an API with libcurl. The proper, HTTP/1.1 compiliant solution will be available in version 1.5, which is in development for years now, but since 1.4.21 they have implemented a solution to behave like a HTTP/1.0 server, which is just what 99.9% of users need.
To fix 417 errors in lighttpd, simply add this to your lighttpd.conf:
server.reject-expect-100-with-417 = "disable"
and restart your lighttpd server. Viola!