yslow fails on multiple backgrounds?

I'm using a noise with a css3 gradient similar to this:

background: url('noise.png'), -moz-linear-gradient(top, #ccc, #ddd);

Works well but now Yslow gives me an error about the expired headers.

There is 1 static component without afar-future expiration date.

 * (no expires) .../noise.png"), -moz-linear-gradient(...), rgb(...

Inside my htac开发者_Go百科cess I'm using this, it worked well on single background(image):

<ifmodule mod_headers.c>
    <filesmatch \.(gif|ico|jpg|png)$>
        header set cache-control max-age=2419200
    </filesmatch>
</ifmodule>

(I already tried it by media type, but this did not work as well)

Maybe you guys already solved this problem!?

I encountered some problems with Yslow as well - told me I wouldn't gzip my files although I did.

Generally CSS's content does not have anything to do with caching/... so if it worked before and you didn't change anything else, changes are there that Yslow failed.

One way to check whether it's working or not would be (supposing you're using chrome):

1. press F12
2. select the network tab
3. select whatever you want
4. view the headers of the file you want to check the headers of ;)