CSS Border render priority - html

Question

I have this problem where Firefox and IE refuse to render a border behind an image no matter what I do, while Chrome and Opera do fine. I've moved the div containing the arrow all over the place, even tried to force it with z-index, but it won't budge. Any advice?
Chrome/Opera and IE/Firefox:
I have a JSFiddle setup here: http://jsfiddle.net/3Lqoxv2r/
CSS:
html {
height: 100%;
background: #eee;
}
body {
background: url(../img/background.jpg);
background-repeat: no-repeat;
background-size: cover;
margin: 0px;
height: 100%;
overflow: hidden;
background-position: center;
font-family: Helvetica;
}
body.welcome {
background: url(../img/welcome_background.jpg);
background-size: cover;
background-position: center;
}
p {
margin: 0px;
}
::-webkit-scrollbar {
width: 1px;
}
.wrapper {
overflow-y: scroll;
height: calc(100% - 90px);
}
header {
position: static;
top: 0;
height: 60px;
}
header .logo {
float: left;
width: 256px;
}
header .logo .container {
padding: 0 0 0 128px;
height: 60px;
background: white;
}
header .logo .container img {
margin: 13px 0 0 0;
width: 63px;
height: 66px;
filter: hue-rotate(0deg);
-webkit-filter: hue-rotate(0deg);
-moz-filter: hue-rotate(0deg);
-o-filter: hue-rotate(0deg);
-ms-filter: hue-rotate(0deg);
}
header .menu {
float: left;
background: white;
width: calc(100% - 256px);
height: 100%;
}
header .menu nav {
float: left;
}
header .menu nav ul {
list-style-type: none;
margin: 0;
padding: 0;
}
header .menu nav ul li {
float: left;
width: 128px;
line-height: 57px;
letter-spacing: -2px;
text-align: center;
font-size: 19px;
text-transform: uppercase;
color: #8a8a8a;
border-top: 3px solid white;
}
header .menu nav ul li.active {
color: #f05555;
border-top: 3px solid #f05555;
}
header .menu .container {
float: right;
padding-right: 128px;
}
.before {
content: "";
position: absolute;
top: 60px;
left: 130px;
border-top: 23px solid white;
border-left: 28px solid transparent;
border-right: 28px solid transparent;
}
div.content {
width: 100%;
height: calc(100% - 90px);
}
div.content .menu {
height: 50px;
}
div.content .container {
overflow-y: scroll;
height: 100%;
margin: 0 128px 0 128px;
width: calc(100% - 256px);
background: white;
}
footer {
position: static;
bottom: 0;
height: 30px;
background: white;
padding: 0 0 0 128px;
line-height: 30px;
font-size: 10px;
color: #8a8a8a;
}

Answer 1

You have used position: static for header tag. Use position: relative instead, it will work in ff and IE11.