'&' and '?' in a URL

How to use '&' and '?' in a URL?

May I do

<cfset str = str & "&lang=fr">

and

<cfset path = "http://" & servername & "/" & path & "?" & str>

as in the following code:

<cfset servername = #cgi.SERVER_NAME#>

<cfset script = #cgi.SCRIPT_NAME#>

<cfset str = #cgi.query_string#>

<cfif find("lang=en", str)>

      <cfset str = ReplaceNoCase(str, "lang=en", "lang=fr")>

<cfelse>

     <cfset str = str & "&lang=fr">

</cfif>

<cfset position = find("TEST", script)>

<cfset length = Len(script)>

<cfset path = Mid(script, position, length)>

<cfset path = "http://" & servername & "/" & path & "?" & str>

<li><div><a href="<cfoutput>#path#</cfoutput>">Fran&ccedil;ais</a></div></li>