Hi
I was looking magento tutorial there I found following lines
<input type="text" name="custom[ssn]" value="<?php echo $this->htmlEscape($this->getQuote()->getSsn()) ?>" title="<?php echo $this->__('SSN') ?>" class="input-text required-entry" id="billing:ssn" />
</div>
can you please explain me what do you mean by
$this->getQuote()->getSsn()
tutorial link is
http://www.excellencemagentoblog.com/magento-add-custom-fields-checkout-page