1. You can visit any url of you Joomla site and add template=protostar at the end to see if the problem is related to the current template YOURSITEURL.com/index.php/shop/melbourne-raceway-merchandise?template=protostar, which in this case it is.
2. Looking at the CSS it looks like you have added the below CSS that seems to be causing the issue, do remove it and it should take care of it.
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