I am trying get the string in the following URL to display on my webpage.
http://example.com?ks4day=Friday+September+13th
EDIT: The date in the URL
If that's what you are doing, the plus sign will not be the only one that is going to give you a hard time. The apostrophe ('), equals (=), plus (+) and basically anything not in the permitted URL characters (see Percent-encoding @ Wikipedia) is going to get escaped.
What you are looking for is the decodeURIComponent function.