Im using "IsNull()" function to check for NULL value,
but I get the following error
Compiler Error Message: BC30451: The name 'IsNull' is not declared.

Source Error:


Line 124:	w = 800
Line 125:	h = 400
Line 126:	if IsNull(ctL) then
Line 127:		If not IsNull(rs("wS")) then w = rs("wS")
Line 128:		If not IsNull(rs("hS")) then h = rs("hS")

Source File: C:\WebServers\Gazeta\default.aspx    Line: 126
Which function should I use?