I can suggest you few workarounds but first can you tell me:
- which version of Sitefinity do you use for your project ?
- do you have a custom master page which you have applied to your website?
Last but not least in importance, can you check the following forum article
which contains valuable information regarding your case.
You can also find the following code useful:
protected void Page_Load(object sender, EventArgs e)
if (this.GetIndexRenderMode() != Telerik.Sitefinity.Web.UI.IndexRenderModes.Normal)
All the best,
the Telerik team