What is & used for
& is HTML for "Start of a character reference".
& is the character reference for "An ampersand".
¤t; is not a standard character reference and so is an error (browsers may try to perform error recovery but you should not depend on this).
If you used a character reference for a real character (e.g. ™) then it (™) would appear in the URL instead of the string you wanted.
(Note that depending on the version of HTML you use, you may have to end a character reference with a ;, which is why &trade= will be treated as ™. HTML 4 allows it to be ommited if the next character is a non-word character (such as =) but some browsers (Hello Internet Explorer) have issues with this).
HTML doesn't recognize the & but it will recognize & because it is equal to & in HTML
I looked over this post someone had made: http://www.webmasterworld.com/forum21/8851.htm