A little help with a back button needed

[red8ii8]

Hi, I'm building my first cart and not fluent in code of any kind, could someone help me with a back button? I don't want the prev/next bar on the product info page, just a back button. When I paste just the first line of the code that calls for the three buttons I get nothing, so I tried to use the code for the back button that shows on many other pages but it just takes you to the home page.

Here's the section I want to change to a plain old "back" button that will take the user to where they were:

<!--bof Prev/Next bottom position -->
<?php if (PRODUCT_INFO_PREVIOUS_NEXT == 2 or PRODUCT_INFO_PREVIOUS_NEXT == 3) { ?>
<?php
/**
 * display the product previous/next helper
 */
 require($template->get_template_dir('/tpl_products_next_previous.php',DIR_WS_TEMPLATE, $current_page_base,'templates'). '/tpl_products_next_previous.php'); ?>
<?php } ?>
<!--eof Prev/Next bottom position -->

This is what i tried that takes them to the home page instead:

<div class="buttonRow back"><?php echo zen_back_link() . zen_image_button(BUTTON_IMAGE_BACK, BUTTON_BACK_ALT) . '</a>'; ?></div>
</div>

An example page is:

http://www.thepearltrader.com/index....products_id=72

thanks for any help!