This parameter represents an unique timestamp and is added to each url on purpose. Since the AJAX requests are using GET verb, those requests might be cached by the browser. This means that when the user clicks on the links, your server might never be reached. The parameter ensures that the responses are not cached, because each time you get an unique url. Currently this is hardcoded in the WebGrid and there's no way to disable it.
Of course if for some reason you want to shoot yourself in the foot and remove this parameter one possibility is to subscribe to a custom AJAX callback:
var grid = new WebGrid(
Model,
ajaxUpdateContainerId: "grid",
ajaxUpdateCallback: "callback"
);
in which you could replace all links and remove the __swhg
parameter:
function callback() {
$('a[data-swhglnk="true"]').attr('href', function () {
return this.href.replace(/&__swhg=[0-9]{13}/, '');
});
}