$(document).ready(function () {
    var Watermark = "Search";
    var SearchBox = $("[id$='_txtSearch']");

    if (SearchBox.val() == "" || SearchBox.val() == Watermark) {
        SearchBox.css("text-align", "center").val(Watermark);
    }

    SearchBox.focus(function () {
        $(this).filter(function () {
            return $(this).val() == "" || $(this).val() == Watermark
        }).css("text-align", "left").val("");
    });

    SearchBox.blur(function () {
        $(this).filter(function () {
            return $(this).val() == ""
        }).css("text-align", "center").val(Watermark);
    });
});