Web Forms :: How To Avoid Save As Dialogue Box In Mac

I am showing pdf documents in my application using a menu, what i am doing is whenever a menu option is clicked for pdf file to view it calls a user control and in that user control i have made an iframe and that iframe calls a page called reference.aspx that calls the following code to show pdf file in that iframe.

MemoryStream Memory = new MemoryStream();
FileStream file = null;
Byte[] buffer = new Byte[10];
buffer = new Byte[file.Length];
file.Read(buffer, 0, (int)file.Length);
Memory.Write(buffer, 0, (int)file.Length);
file.Close();
HttpContext.Current.Response.ContentType = "application/pdf";
HttpContext.Current.Response.AddHeader("content-disposition", "inline; filename=" + selectedReport);
HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
HttpContext.Current.Response.BinaryWrite(Memory.ToArray());
HttpContext.Current.Response.Flush();
Memory.Dispose();

It works great in windows environment, in IE and firefox etc but when it is run in MAC it does not open file in browser rather it opens a save as dialogue box that i don't want, i want to show is that file.