Hola haber si así lo solucionas:
Código HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Prueba</title>
<style>
body {
background-color: #fff;
margin: 0 0 0 0;
}
.topbar-line{
width: 100%;
background: #fff;
text-align: center;
height: 3px;
background-color:#2b813b;
}
.contenedor-topbar{
width: 326px;
height: 26px;
margin: 0 auto;
}
.topbar-middle{
height: 26px;
width: 300px;
float:left;
background-color: #2b813b;
}
.triangulo_top_right {
width: 0;
height: 0;
float:left;
border-top: 26px solid #2b813b;
border-right: 13px solid transparent;
}
.triangulo_top_left {
width: 0;
height: 0;
float:left;
border-top: 26px solid #2b813b;
border-left: 13px solid transparent;
}
</style>
</head>
<body>
<div class="topbar-line"></div>
<div class="contenedor-topbar">
<div class="triangulo_top_left"></div>
<div class="topbar-middle">Prueba de Topbar</div>
<div class="triangulo_top_right"></div>
</div>
</body>
</html>