Hi,
The small amount of javascript HikaShop in the header of the page is not something which would slow the page display. It's nothing compared to all the javascript of all the javascript files loaded by joomla/the template/other extensions in the header.
Also, the HTML footer tag is not to be used to include javascript on the page, and on top of that, it's not supported by IE7 and IE8:
www.w3schools.com/tags/tag_footer.asp