I recommend changing
string sLink = this.BasePath + "editor/fckeditor.html?InstanceName=" + this.ClientID ;
to
string sLink = this.ResolveUrl(this.BasePath) + "editor/fckeditor.html?InstanceName=" + this.ClientID ;
so that if the BasePath is say "~/" it will map correctly to the web application's virtual directory.
string sLink = this.BasePath + "editor/fckeditor.html?InstanceName=" + this.ClientID ;
to
string sLink = this.ResolveUrl(this.BasePath) + "editor/fckeditor.html?InstanceName=" + this.ClientID ;
so that if the BasePath is say "~/" it will map correctly to the web application's virtual directory.