Tres,
I've created a jQuery plugin that can simplified the development for template for printing. and can be used to show preview what will be printed.
for example, to print a box of 10 character spaces, you can use :
<table width="10"><tr><td>tes</td></tr></table>
<div class="dPrint topLeft drawLine[repeat[10]] topRight newLine">
<div class="dPrint vLine"></div><div class="dPrint format[left[10]]">tes</div><div class="dPrint vLine newLine"></div>
<div class="dPrint bottomLeft drawLine[repeat[10]] bottomRight newLine"></div>
<script>
directPrint.setPrinterName('LX300');
directPrint.init('.dPrint'); //this is simply a jQuery selector
//directPrint.printFile('logo.prn'); -> to print image .prn
directPrint.print();
</script>
the plugins can even extended to print character that hadn't been included in the first place.
It can clip the text if the content is longer than reserved space.
It's been used with jquery-1.5.2 and jquery-1.4.3.
I know that the sample is seem to simple and is worthless, but I've been using it to print billing and invoice.
if anyone is interesed I'm happy to give more complex examples