Apache -> No size for images

[nicmic]

Hi,

I have a big problem on my site: the images are not cached by clients. I think it is because my server doesn't send the file size for images. But why?

If, in my browser, I do a right click on a image and select "properties", size is "unavailable" on my site. But on every other site I can see the file size.

Can somebody help me?

Thanks