table sorter not working

Question 1

You forgot to close a script tag </script> :

<script src="http://tablesorter.com/__jquery.tablesorter.min.js" type="text/javascript"/>

Correct markup :

<script src="http://tablesorter.com/__jquery.tablesorter.min.js" type="text/javascript"/></script>

I copied you code, added </script> and it works for me. Also jquery file from http://tablesorter.com/jquery-latest.js is really outdated (2008), consider using other cdn like //code.jquery.com/jquery-1.10.2.min.js or googleapis

Question 2

You need to customize with tablesorter options. Here is example http://jsfiddle.net/dhana36/BKgue/184/

$('.tablesorter').tablesorter({
    // *** Appearance ***
    // fix the column widths
    widthFixed : true,
    // include zebra and any other widgets, options:
    // 'uitheme', 'filter', 'stickyHeaders' & 'resizable'
    // the 'columns' widget will require custom css for the
    // primary, secondary and tertiary columns
    widgets    : [ 'uitheme', 'zebra' ],
    // other options: "ddmmyyyy" & "yyyymmdd"
    dateFormat : "mmddyyyy",

    // *** Functionality ***
    // starting sort direction "asc" or "desc"
    sortInitialOrder : "asc",
    // These are detected by default,
    // but you can change or disable them
    headers : {
        // set "sorter : false" (no quotes) to disable the column
        0: { sorter: "text" },
        1: { sorter: "digit" },
        2: { sorter: "text" },
        3: { sorter: "url" }
    },
    // extract text from the table - this is how is
    // it done by default
    textExtraction : {
        0: function(node) { return $(node).text(); },
        1: function(node) { return $(node).text(); }
    },
    // forces the user to have this/these column(s) sorted first
    sortForce : null,
    // initial sort order of the columns
    // [[columnIndex, sortDirection], ... ]
    sortList : [[3,0]],
    // default sort that is added to the end of the users sort
    // selection.
    sortAppend : null,
    // Use built-in javascript sort - may be faster, but does not
    // sort alphanumerically
    sortLocaleCompare : false,
    // Setting this option to true will allow you to click on the
    // table header a third time to reset the sort direction.
    sortReset: false,
    // Setting this option to true will start the sort with the
    // sortInitialOrder when clicking on a previously unsorted column.
    sortRestart: false,
    // The key used to select more than one column for multi-column
    // sorting.
    sortMultiSortKey : "shiftKey",

    // *** Customize header ***
    onRenderHeader  : function() {
        // the span wrapper is added by default
        $(this).find('span').addClass('headerSpan');
    },
    // jQuery selectors used to find the header cells.
    selectorHeaders : 'thead th',

    // *** css classes to use ***
    cssAsc        : "headerSortUp",
    cssChildRow   : "expand-child",
    cssDesc       : "headerSortDown",
    cssHeader     : "header",
    tableClass    : 'tablesorter',

    // *** widget css class settings ***
    // column classes applied, and defined in the skin
    widgetColumns : { css: ["primary", "secondary", "tertiary"] },
    // find these jQuery UI class names by hovering over the
    // Framework icons on this page:
    // http://jqueryui.com/themeroller/
    widgetUitheme : { css: [
        "ui-icon-arrowthick-2-n-s", // Unsorted icon
        "ui-icon-arrowthick-1-s",   // Sort up (down arrow)
        "ui-icon-arrowthick-1-n"    // Sort down (up arrow)
        ]
    },
    // pick rows colors to match ui theme
    widgetZebra: { css: ["ui-widget-content", "ui-state-default"] },

    // *** prevent text selection in header ***
    cancelSelection : true,

    // *** send messages to console ***
    debug : false
});