[Alan]

Hi Disneyana,

In case if you don't want to create another CSS file, because you basically want to add a dark background to your checkout page.

I'm assuming you're using dialog.tpl to display your cart.php frames.

In your dialog.tpl,

<TABLE border=0 cellPadding=2 cellSpacing=0 {$extra}>
<TR> 
<TD height="20" class=DialogTitle background="{$ImagesDir}/dialog_bg.gif" valign=bottom>{$title}</TD>
</TR>
<TR><TD class=DialogBorder><TABLE border=0 cellPadding=10 cellSpacing=0 width="100%">
<TR>
{*==============================*}
{if $mode eq "checkout"}
<TD class=DialogBoxCSSForYourDarkBackGround>
{else}
<TD class=DialogBox>
{/if}
{*==============================*}
{$content}

</TD></TR>
</TABLE></TD></TR>
</TABLE>

CSS file:

.DialogBoxCSSForYourDarkBackGround {
             background-color: your-dark-color;
             color: opposite-of-your-dark-color
}

I hope that is what you're looking for. If not, then please ignore my rambling.

Have a good night!