Displaying a "+" sign

I'm baffled. I have a program (written in PeopleCode, similar to BASIC) that is creating URLs. There are two functions. The first one writes a URL with no repetition in it. At a few places in the code, I have it insert "+" into a string (technically I'm concatenating string1 | "+" | string2, This produces a URL with a plus sign, +, in the middle, and at least on Firefox and IE 9, it works fine.
I get this at the end of the URL, as I am supposed to do. "&getbooks=display+books"

When I...

Displaying a "+" sign