Query String is one of the caching technique used in asp.net to speed the process of response to repeated requests. It has the followings plus and minus.
Plus
1. It doesnt require any server side resources.
2. All the browsers supports.
Minus
1. The information is passed along with the url making it visible to all.
2. The browser import a constraint of specific size on this hence only
restricted size of data could be passed.