Question

The grid works regularly when using the select at normal view, 100%, however if changing the size to a smaller or the zoom, the select does not work properly. On the other hand, the option check works perfectly at any views

example http://jsfiddle.net/mutesex/czxgg/2/

$("#slider").slider({
  value: 1,
  min: 0.1,
  max: 2,
  step: 0.1,
  slide: function (event, ui) {
    $("#amount").html("" + parseInt((ui.value) * 100) + "%");
    $('#<%= GridView1.ClientID%>').animate({ zoom: ui.value }, 1);
      //selectable___();
  }
});

$("#amount").html("100%");

function selectable___() {
  $(document).ready(function () {
    $("#<%= GridView1.ClientID%>").selectable({
     filter: "td[free='yes']",

     stop: function () {
     var result = $("#select-result").empty();
     $(".ui-selected", this).each(function () {
       var dia__ = $(this).attr("infodia");
       if (!ExisteItem(dia__)) {
         result.append(" #" + dia__);
         diasSeleccion.push({ infodia: dia__ });
       }
     });
   },
   unselected: function (event, ui) { var e = $(ui.unselected); removeItem(e.attr("infodia")); },
   unselecting: function (event, ui) { var e = $(ui.unselecting); removeItem(e.attr("infodia")); }
   });  
  }); 
};

Answer 1

Do not use zoom, selectable widget ignores it. Instead set height and width on slider change.

Remove !important from following widths and heights in your css

    .cell
    {
        ...
        width: 200px;
        ...
    }
    .cellcalday
    {
        ...
        height: 100px;
        ...
    }
    .cellcalfds
    {
        ...
        height: 100px;
        ...
    }

Change your script like this

            $("#slider").slider({
            value: 1,
            min: 0.1,
            max: 2,
            step: 0.1,
            slide: function (event, ui) {

                $("#amount").html("" + parseInt((ui.value) * 100) + "%");
                //$('#ctl00_container_GridView1').animate({ zoom: ui.value }, 1);
                $("table#ctl00_container_GridView1 tr td.cell").css('width', Math.round(200 * ui.value));
                $("table#ctl00_container_GridView1 tr th.cell").css('width', Math.round(200 * ui.value));
                $("table#ctl00_container_GridView1 tr td.cellcalday").css('height', Math.round(100 * ui.value));
                $("table#ctl00_container_GridView1 tr td.cellcalfds").css('height', Math.round(100 * ui.value));

            }
        });

jsFiddle here: http://jsfiddle.net/Ten4u/