Panasonic FP Web-Server2 Hardware And Configuration Manual page 96

HTTP server functions/web pages
If an HTML page from the FP Web-Server is requested by the browser, but
the PLC data cannot be read out from the PLC (wrong baud rate, problems
with cables...), an HTML page with an error message will be displayed
instead of the requested page.
If an HTML page with PLC data shows Err 1 then the field length of the data
is too low. E.g. {DT200_5_ld} and the value of DDT200 is 31235933. So
the value has 8 digits, but the webpage can only display 5 digits because of
the entry _5_ld. Change the field length e.g. to {DT200_12_ld}.
FP Web-Server V2.810 EN 95