Hi,
for the problem, you must create theme for each web browser. Example create theme for IE and Firefox. When you create finish theme for all web browser. you must use code like this.
Protected Sub Page_PreInit(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreInit
If (Request.Browser.Browser.Equals("IE") And Request.Browser.MajorVersion >= 5) Then
Page.Theme = "IE"
Else
Page.Theme = "Firefox"
End If
End Sub
Don't use code above in page master.
Thank you,
Kimsea