Icons Not Visible On All Computers

Recently I reviewed what my website looked like on several different computers and using several different browsers.

With that said, here are some issues I noticed:
– On 2 out of 4 computers I tried the website on, the icons did not show up (I was using IE). By icons, I am referring to: the mail image in the lower right hand corner, the arrow buttons on the rev slider, etc. Is this a java script issue? Is there anything I can do from my perspective to fix these issues and so my website can be more consistent among browsers?

Any help would be appreciated.