picasarapid.aspx
<%@ Page Title="Test_Picasa_Album.aspx" Language="C#" AutoEventWireup="true" %>

<%@ Register TagPrefix="mod" TagName="album" Src="~/Mod/Mod_Picasa.ascx" %>

<script runat="server">
    protected void Init()
    {
        mod_mod_picasa_ascx mod = (mod_mod_picasa_ascx)LoadControl("~/Mod/Mod_Picasa.ascx");
        mod.patg = DDL_Year.SelectedValue;
        mod.type = "content";
        mod.Target = "frame_details";
        mod.rss = "https://picasaweb.google.com/data/entry/base/user/rapidfranz";
        PlaceHolder_Gallery.Controls.Add(mod);
    }
    protected void Page_Load()
    {
        if (!IsPostBack)
        {
            Init();
        }
    }
    protected void DDL_Year_SelectedIndexChanged(object sender, EventArgs e)
    {
        Init();
    }
</script>

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title></title>
    <link href="/css/mod.css" rel="stylesheet" />
</head>
<body>
    <form id="form1" runat="server">
        <table style="width:100%;">
            <tbody>
                <tr>
                    <td colspan="2" style="text-align: right;">
                        <asp:DropDownList runat="server" 
                            ID="DDL_Year" 
                            AutoPostBack="true"
                            OnSelectedIndexChanged="DDL_Year_SelectedIndexChanged">
                            <asp:ListItem Value="2013">2013</asp:ListItem>
                            <asp:ListItem Value="2012">2012</asp:ListItem>
                        </asp:DropDownList>
                    </td>
                </tr>
                <tr>
                    <td>
                        <iframe
                            style="border-width:0pt;"
                            name="frame_details"
                            width="780"
                            height="650"
                            src="http://kdf.iam.at/portals/kdf.iam.at/images/kdf.htm"></iframe>
                    </td>
                    <td>
                        <div style="width:100%; height:650px; overflow:scroll;">
                            <asp:PlaceHolder runat="server" ID="PlaceHolder_Gallery" />
                        </div>
                    </td>
                </tr>
            </tbody>
        </table>
    </form>
</body>
</html>