Data structures in functional languages behave exactly in this way:

http://en.wikipedia.org/wiki/Purely_functional#Examples_of_purely_functional_data_structures

I use an ad-blocker and the main reason is Ars!

I never used an ad-blocker, but their advertising was so intrusive that an ad-blocker was a necessity to be able to read their news on a netbook with a small screen.

You have two options:

The first: be the BOFH and laugh at the stupid users, who do not read/understand the error.

The second: be the smart programmer and anticipate user errors.

This means that for typical user errors you should provide a concise description of the problem and a text explaining how to correct the problem.

Example:

"The date you entered is wrong." should be "The date you entered cannot be parsed. Please provide the date in the format YYYY/MM/DD, e.g. 2009/12/12".

Of course, if an error pops up multiple time a day, it may be that the software is not very intuitive.