Why I use MsgBox in ASP program, program error say without permission

Answer because the ASP is the server running, if you can display a dialog box on the server, then you have to wait for someone to confirm, your program can continue to execute, and the general server will not be guarded, so Microsoft had to ban this function, and told you at random (:) OH) No permissions. However, ASP and client-side scripting can be combined to display a dialog box, as follows:
<% yourvar= "Test dialog box"%>
<% script language= ' JavaScript ' >
Alert ("<%=yourvar%>")
</script>