Has to do with the fact that QueryString encoding prevents it. See
here. Which is more removing it, then preventing it.
Any for one of the reasons it should be obvious.
QueryString retrieves a
string and a means of
concatenating two strings together is with a
+ or
& depending on the language.
Sorry this is a crude explaination, but that is the best I had at the end of a long hard day.
Hope this helps!