Template is different in Explorer & Firefox

Hi, I hope somebody can help. I’m in the process of doing a website for my art and found a free wordpress template i like. However it looks fine in firefox but if i open the site up in explorer every single heading and title disappears! The site is https://www.dogartists.co.uk Does anyone know how to fix this?

Secondly on pages that use the default template it automatically adds “leave a reply” etc at the bottom of the page. Is there a way you can stop this from happening. it’s fine for blog posts but for a website page, not so good. Any help would be much appreciated as wordpress is v new to me and it seems i’m hopeless.