How can I show two background images, using internet explorer 6?

I need to show two background images. I'm doing this:

table.grid thead.grid-header th
{
    background: url('../images/up-down-arrow.gif') no-repeat center right, url('../images/tt-caption-light.gif') repeat;
}

This work fine in internet explorer 11, but I need to do this for internet explorer 6. How can I resolve it? Thank you very much!

via Chebli Mohamed