Hi chetan,
Refer below sample.
Acording to your requirement change css.
HTML
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<style>
body
{
margin: 0;
}
.content
{
position: absolute;
top: 100px;
background: rgba(0, 0, 0, 0.5);
color: #f1f1f1;
left: 40px;
}
#myVideo
{
object-fit: initial;
width: 100%;
height: 300px;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<div>
<video autoplay muted loop id="myVideo">
<source src="Bunny.mp4" type="video/mp4">
Your browser does not support HTML5 video.
</video>
</div>
<div class="content">
Search :
<asp:TextBox ID="txtSearch" runat="server"></asp:TextBox>
<asp:Button Text="Search" runat="server" />
</div>
</form>
</body>
</html>
Sreenshot
