Read URL GET variable

gistfile1.js

// Given a query string "?to=email&why=because&first=John&Last=smith"
// getUrlVar("to")  will return "email"
// getUrlVar("last") will return "smith"

// Slightly more concise and improved version based on http://www.jquery4u.com/snippets/url-parameters-jquery/
function getUrlVar(key){
	var result = new RegExp(key + "=([^&]*)", "i").exec(window.location.search); 
	return result && unescape(result[1]) || ""; 
}

// To convert it to a jQuery plug-in, you could try something like this:
(function($){
	$.getUrlVar = function(key){
		var result = new RegExp(key + "=([^&]*)", "i").exec(window.location.search); 
		return result && unescape(result[1]) || ""; 
	};
})(jQuery);

I'm new to this so I apologize if this is obvious to some....

But how do I call getUrlVar(key) and use the result in another link
on my html page?

For example: http://FirstUrl.com/?id=123456

I need to extract the id (123456) from the First Url and use that
in my Second Url so the link is Clickable.

href=http://SecondUrl.com/?id=123456

Any help gratefully accepted, it's driving me nuts!!!

Thank you! THANK YOU! This helped me so much!