In your master page, you can have
<!-- in Master Page -->
<head runat="server">
<link href="Style.css" rel="stylesheet" type="text/css" />
<asp:ContentPlaceHolder ID="header" runat="server">
</asp:ContentPlaceHolder>
</head>
In your view page, you can add more into the header,
<!-- in view Page -->
<asp:Content ID="viewContent" ContentPlaceHolderID="header" runat="server">
<link href="Style1.css" rel="stylesheet" type="text/css" />
</asp:Content>
The final page will be rendered as
<head runat="server">
<link href="Style.css" rel="stylesheet" type="text/css" />
<link href="Style1.css" rel="stylesheet" type="text/css" />
</head>