You aren't changing it. You are representing it in a URL.

In morse code the data "s" is represented as "...".
In URLs, the data "&" is represented as "%26"

Edit: Having reread the grandparent I now see I'm being stupid. The grandparent is good style advice, but sometimes changing things after the fact is a little difficult - especially on a short time scale. You can encode the names as well as the values of parameters though.