To solve the issue, you are using the z-index on the footer and header, but you forgot about the position, if a z-index is to be used, the element must have a position:
Add to your footer and header this CSS:
position: relative;
EDITED:
Also noticed that the background image on the #backstretch has a negative z-index, don’t use that, some browsers get really weird…
Remove From the #backstretch:
z-index: -999999;
Read a little bit about Z-Index here!