Advice Needed

Hi Guys,
I'm 16 and recently designed a site as a hobby. I have no experience in webdesign and basically learnt everything from forums, luck and a lot of searching. It's an e-commerce site which I intended to be a challenge for me and already I have learnt a lot.

I am still obviously very inexperienced at this and don't know the finer details that go into making a great website, like I'm sure many of you do.
I would therefore like to ask if you could take a look at my site and tell me what's wrong with it, I'm dying to get some feedback and would love to hear a professional opinion.

Like I said, I'm not here to try and promote my site, I'm here to learn and welcome any constructive criticism and opinions that you may have.
Thank you all for your time, I really appreciate it!
The site is http://herostore.net