An error is thrown when RadButton NavigateUrl is defined in content page with tilde and the master page is up one level. Workaround: Remove the tilde from the navigate url.
Another workaround is setting the NavigateURL on RadButton_Load event:
protected void RadButtons_Load(object sender, EventArgs e)
{
(sender as RadButton).NavigateUrl = this.ResolveUrl((sender as RadButton).NavigateUrl);
}
<telerik:RadButton runat="server" ID="RadButton1" ButtonType="StandardButton" NavigateUrl="~/App/Home.aspx" Text="Home" OnClick="RadButton1_Click" OnLoad="RadButtons_Load" AutoPostBack="true" />