css特定区域不随滚动条滚动

.area1{ 
 top: 0;
 width: 100%; 
 position: fixed; 
 _position: absolute;
 z-index: 999; 
 background-color: white;
} 
.area2{ 
 width: 100%;
 position: relative; 
 top: 85px; 
}

area1固定，area2可滚动，且滚动至area1区域时内容被覆盖（将背景颜色去掉可共存）；