Many HTTP Error 416 Requested Range not satisfiable

[Patkob]

Hello,

I'm getting many HTTP 416 errors on my site, and I don't know what to
do with them (and maybe how to fix/avoid them).

For example, these are some $_SERVER[] vars from one of the requests:

[REQUEST_METHOD] => GET
[REQUEST_URI] => /gfx/glow.png
[SERVER_SOFTWARE] => nginx/0.7.67
[HTTP_USER_AGENT] => Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US)
AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7
[HTTP_ACCEPT_ENCODING] => gzip,deflate,sdch
[HTTP_ACCEPT_LANGUAGE] => pl-PL,pl;q=0.8,en-US;q=0.6,en;q=0.4
[HTTP_ACCEPT_CHARSET] => ISO-8859-2,utf-8;q=0.7,*;q=0.3
[HTTP_RANGE] => bytes=20201-
[HTTP_IF_RANGE] => Sat, 13 Nov 2010 13:44:04 GMT

Interesting thing is, the file "/gfx/glow.png" is exactly 20201 bytes
long, so WHY is client's browser trying to download more? Is that some
cache checking?

What should I send to client when this error occurs?

thanks
p.