web.config error - system.web.extensions cannot be read missing

Just tried to update the binding of a site about to give live based on Umbraco 4.7 and got "system.web.extensions cannot be read missing" bla bla

Just had to add to the configsections:

Jquery entertainments calendar

I needed to build a funky navigation with an AJAX driven events calendar. This would have two stages, an overview showing thehighlighted events and then adetailed listing

Each months events should fade into the next, have a preloader and be driven by an aspx page so passing of the month clicked would be needed.

Once ona ,months highlighted events, a button to fade this into the detailed listing again driven by an aspx page

1) For the funky navigation I decided on the lavalamp jquery effect

http://www.gmarwaha.com/blog/2007/08/23/lavalamp-for-jquery-lovers/

Very easy to implement and get a simple and subtle effect

2) Next I needed to fde the content, show a preloader and then fade back in the new content

$('ul.lavaLamp a').click(function() {
     hashid = this.id
     $('#calendar').html('preloader here');
    $('#calendar').fadeOut("fast", function () {
    $(this).load("calendar_content.aspx",{"month":hashid}).fadeIn("slow");
    });
    }, 10000);

Get your ajax preloader gif here http://www.ajaxload.info/

This needs to show the preloader in a new div but it looks pretty mucvh how I wanted

3)

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I have re-written this to work properly now - code to follow