Cache Control Headers

I am using a controller to serve up CSS. I am having a problem with
browsers not caching the CSS and think it is related to the Cache-
Control header. I tried the following, but the browsers still will
not cache:

headers['Cache-Control'] = 'public'

Any ideas?

Thanks,
Tom

2 questions:

1) do you have caching disabled (sorry but tech support always has to
know if the computers plugged in).
2) If in firefox you go to Tools/page_info what are the values of:

-Cache Source
-Expires
-Meta

Thanks so much for looking into this with me! I'm getting desperate.

2 questions:

1) do you have caching disabled (sorry but tech support always has to
know if the computers plugged in).

Yes, and have a used all browsers with the same the results.

2) If in firefox you go to Tools/page_info what are the values of:

All of the results are taken from looking at the information on the
css being linked on the page using the following link:
  <link href="/css/colorpicker.css" media="screen" rel="stylesheet"
type="text/css" />

The following results are using the Rails default headers:
  Cache Source: Disk cache
  Expires: Not specified
  Meta: [nothing]

  Also, the response headers (according to the web developer plugin):
    Status: 304 Not Modified
    X-Runtime: 0.08278
    Etag: "aeafc040943fac69eb986a0f90e79063"
    Cache-Control: private, max-age=0, must-revalidate
    Server: Mongrel 1.0.1
    Content-Type: text/css; charset=utf-8
    Content-Length: 2452
    200 OK

The following results are after I have switched the headers['Cache-
Control'] to 'public':
  Cache Source: Disk cache
  Expires: Not specified
  Meta: [nothing]

  Also, the response headers (according to the web developer plugin):
    Status: 304 Not Modified
    X-Runtime: 0.08174
    Etag: "aeafc040943fac69eb986a0f90e79063"
    Cache-Control: public
    Server: Mongrel 1.0.1
    Content-Type: text/css; charset=utf-8
    Content-Length: 2452
    200 OK

I'm having the same problem. I'm working on an app and deploying to a
development server and I noticed recently that css background images are
being reloaded on every page request. At first I thought it was my
browser but then I checked the headers and I find that they're not
allowing caching:

Server: nginx/0.5.26
Content-Type: text/html; charset=utf-8
Status: 304 Not Modified
X-Runtime: 0.01267
Etag: "fd433ad7994a671e38210f06ac18cfbf"
Cache-Control: private, max-age=0, must-revalidate
Content-Encoding: gzip

200 OK

I'm not sure whether to change the Rails config or the Ngninx server
config? Which would be correct? I'm not sure where this header is being
set so I don't know where to tackle the problem.