Step 1: put this code in your "head" tags area, or somewhere above where you're going to call the script.

<script>

 // This script is for use with Cafepress ad banners. This particular script defaults to the
// large CP banner, but you can easily make changes to it in the "adtext" field below.
// Jim, Teesed.com
// For questions or suggestions, please post on CP message board
// http://forums.cafepress.com/groupee/forums?a=tpc&s=8101...=80810172&r=25210272

function checkSaleDate(firstdate,lastdate)
{

// Change the variables below for your storeid and any alternative html to show. 
// Remember that any single quotes have to be preceded by a backslash.
// You have 3 required changes

// Change #1 - Replace "yourshopid" with your actual shopid

    shopid = 'yourshopid';

// Change #2. Select your sale banner size selection
// Remove the two slashes (//) to select your banner size, and 
// make sure there are two slashes in front of the other three choices.

	adchoice = 1;  // large 468 x 60 banner
//	adchoice = 2;  // square 125 x 125 banner
//	adchoice = 3;  // small 120 x 60 banner
//	adchoice = 4;  // extra long 750 x 40 banner provided by hecticstudios.com

// Change #3) Put the alternative text you want to display before or after sale dates.
// This can be actual text, html code for an alternative image banner, or just put '' to show nothing.

    alttext = '';

// no need to change anything below this line if you don't want

// Ad banner text to display between firstdate and lastdate

	if (adchoice == 1) 
	{
    	adtext = '<a href="http://www.cafepress.com/' + shopid + '"><img src="http://www.cafepress.com/content/banners/promo_468x60_01.gif" width="468" height="60" alt="Store Sale Banner" border="0"></a>';
	} 
	else if (adchoice == 2) {
    	adtext = '<a href="http://www.cafepress.com/' + shopid + '"><img src="http://www.cafepress.com/content/banners/promo_125x125_01.gif" width="125" height="125" alt="Store Sale Banner" border="0"></a>';
	}
	else if (adchoice == 3) {
    	adtext = '<a href="http://www.cafepress.com/' + shopid + '"><img src="http://www.cafepress.com/content/banners/promo_120x60_01.gif" width="120" height="60" alt="Store Sale Banner" border="0"></a>';
	}
	else if (adchoice == 4) {
		adtext = '<a href="http://www.cafepress.com/' + shopid + '"><img src="http://www.hecticstudios.com/salebanner.gif" width="750" height="40" alt="Store Sale Banner" border="0"></a>';
	
	}
	else { // just in case an ad choice hasn't been made, or it is something other than 1 - 4
    	adtext = '<a href="http://www.cafepress.com/' + shopid + '"><img src="http://www.cafepress.com/content/banners/promo_468x60_01.gif" width="468" height="60" alt="Store Sale Banner" border="0"></a>';
	}
	
	
    var startdate = new Date(firstdate);
    var enddate = new Date(lastdate);
    var today = new Date();
    
    if ((today >= startdate) && (today <= enddate))
        {
        document.write (adtext);
        }
    else
        {
        document.write (alttext);
        }

} //function checkSaleDate()

</SCRIPT>

Step 2: place this text block in your web page wherever you want the ad banner to appear --
-- don't forget to change the start and end dates to match the upcoming sale --

<SCRIPT LANGUAGE="JavaScript">
checkSaleDate("1/15/2005","5/13/2006");
</SCRIPT>