What does this error mean, how to avoid it and how to solve it.

"HTTP Web Server: Lotus Notes Exception - @Function is not valid in this context"

This occurs on a browser and means that the form being used is trying to use a Notes Client compatible @formula command when they are not appropiate.

The most common one is @prompt.

How to Avoid

To avoid them use something like:

@if(@iserror(r) & @clienttype="Notes";

@return( @prompt([ok];"Error";"Field name"));

@iserror(r);

@return("Error in field Name");

"");

This code displays a a prompt message if the form is being used in notes otherwise it puts a message in the field.

How to Find the Field

This is a painful process, first check your fields for likely suspects, if you have lots of fields then make a copy of the form, then remove 5 or six fields starting from the bottom of the form then test it again on the web. If the error goes away, then you know the error was in those five fields. If not remove a few more again from the bottom of the fom, then test again.