Hi telerik team,
Thank you for a quick response. I used RadTreeView for ASP.NET on IE 6. Anyhow this problem doesn’t appear on FireFox and IE 7.
Details: The demo of the tree view control didn’t show this issue on IE 6 but it appeared in my application when I moved control on ASP.Net Web Form that has a master page in IE 6 only. It worked perfect without master page in IE 6. Also same application with/without master page works fine in FireFox and IE7.