You should include that
link
tag in master page itself. If you want to do it with content page, you need to add it via code.
Protected Sub Page_Load(ByVal sender As Object, _
ByVal e As System.EventArgs)
Dim cssLink As New HtmlLink()
cssLink.Href = "~/styles.css"
cssLink.Attributes.Add("rel", "stylesheet")
cssLink.Attributes.Add("type", "text/css")
Header.Controls.Add(cssLink)
End Sub
IMO, you should place your
link
tag in master page within
head
.