设置标题中h1元素的上边距不能按预期工作

I have made use of the html5 header tag and an h1 tag within it. After setting up the top margin property of the h1 element in my header to 0px, i manage to remove the top margin of the header, but i want the h1 element inside my header to have a top margin of around 15px.I have made use of the html5 header tag and an