Make sure to include one OPCWebRefresh component in each WebForm you will be using OPC Web Trend components for real-time update. Leave the name of the OPCWebRefresh ID as OPCWebRefresh1. Only one OPCWebRefresh component is needed per from. You are welcome to set the Refresh property to anything you desire as low as 100 milliseconds, but the amount of CPU load used on each browser will be dependent on the amount of data to display.
If IIS was not setup when OPC Systems.NET was installed with OPC Web Trend.NET you can easily un-install and re-install OPC Systems.NET or manually create a directory in your IIS root directory (C:\Inetpub\wwwroot\) with the name OPCWebTrendImages.
Then using the Windows Command Prompt (cmd.exe) run the following command to give modify rights to the ASPNET user account to the OPCWebTrendImages directory you have just manually created.
Cacls.exe “[RUNTIMEIMAGES]” /T /E /C /G “[COMPUTERNAME]\ASPNET”:C
[RUNTIMEIMAGES] is the path for the OPCWebTrendImages folder usually C:\Inetpub\wwwroot\OPCWebTrendImages.
[COMPUTERNAME] is the name of your computer.