With HTML 5, you need to simply add an id attribute to your <div> with a value of product. This needs to be a unique id attribute within the page (for all elements):
<div id="product">
See the working draft.
In HTML 4.01 you need to use an anchor tag with a name just above your target div, or any other element with an id attribute in the other page:
<a name="product"></a>
<div>...
See the HTML 4.01 spec.
Note: The name attribute has been deprecated in the XHTML 1.0 spec.
So, this would be a better option, as it would work for HTML 4.01, XHTML 1.0 and HTML 5:
<div id="product">