By default, all columns in jqGrid can be sorted. This is controlled by the column Sortable property, true by default. Just set it to false and sorting will be disabled for this column.

In this example, only the last column (Freight) can be sorted.

...
<trirand:JQGrid runat="server" ID="JQGrid1" DataSourceID="SqlDataSource1" Width="600px">
<Columns>
<trirand:JQGridColumn Sortable="false" DataField="OrderID" HeaderText="Order ID" PrimaryKey="True" />
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="default.aspx.cs" Inherits="JQSuiteASPNETExample.examples.sorting.disable._default" %>
<%@ Register Assembly="Trirand.Web" TagPrefix="trirand" Namespace="Trirand.Web.UI.WebControls" %>

<!DOCTYPE html>
<html lang="en-us">
<head id="Head1" runat="server">
    <meta charset="utf-8">
    <title>jqGrid for ASP.NET WebForms - disable sorting</title>
    <!-- The jQuery UI theme that will be used by the grid -->
    <link rel="stylesheet" type="text/css" media="screen" href="http://code.jquery.com/ui/1.12.1/themes/redmond/jquery-ui.css" />
    <!-- The jQuery UI theme extension jqGrid needs -->
    <link rel="stylesheet" type="text/css" media="screen" href="/themes/ui.jqgrid.css" />
    <!-- jQuery runtime minified -->
    <script src="/js/jquery-3.2.1.min.js" type="text/javascript"></script>
    <!-- The localization file we need, English in this case -->
    <script src="/js/trirand/i18n/grid.locale-en.js" type="text/javascript"></script>
    <!-- The jqGrid client-side javascript -->
    <script src="/js/trirand/jquery.jqGrid.min.js" type="text/javascript"></script>
    <!-- This jQuery UI reference is needed only for the demo (code tabs). jqGrid per se does not need it. -->        
    <style type="text/css">
        body, html { font-size: 80%; }    
    </style>
</head>
<body>
    <form id="form1" runat="server">    
        
    <asp:SqlDataSource runat="server" ID="SqlDataSource1" 
        ConnectionString="<%$ ConnectionStrings:SQL2008_661086_trirandEntities %>"                 
        SelectCommand="SELECT [OrderID], [RequiredDate], [ShipName], [ShipCity], [Freight] FROM [Orders]">
    </asp:SqlDataSource>        
        
    <trirand:JQGrid runat="server" ID="JQGrid1" DataSourceID="SqlDataSource1" Width="600px">
        <Columns>
            <trirand:JQGridColumn Sortable="false" DataField="OrderID" HeaderText="Order ID" PrimaryKey="True" />
            <trirand:JQGridColumn Sortable="false" DataField="RequiredDate" DataFormatString="{0:d}"/>
            <trirand:JQGridColumn Sortable="false" DataField="ShipName" />
            <trirand:JQGridColumn Sortable="false" DataField="ShipCity" />
            <trirand:JQGridColumn DataField="Freight" />
        </Columns>
        <SortSettings InitialSortColumn="RequiredDate" InitialSortDirection="Asc" />
    </trirand:JQGrid>
    
    <br /><br />
    <trirand:codetabs runat="server" id="tabs"></trirand:codetabs>     
    
    </form>
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace JQSuiteASPNETExample.examples.sorting.disable
{
    public partial class _default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }
    }
}
Switch theme:


Theming is based on the very popular jQuery ThemeRoller standard. This is the same theming mechanism used by jQuery UI and is now a de-facto standard for jQuery based components. The benefits of using ThemeRoller are huge. We can offer a big set of ready to use themes created by professional designers, including Windows-like themes (Redmond), Apple-like theme (Cupertino), etc. In addition to that any jQuery UI controls on the same page will pick the same theme.

Last, but not least, you can always roll your own ThemeRoller theme, using the superb Theme Editor

To use a theme, simply reference 2 Css files in your Html <head> section - the ThemeRoller theme you wish to use, and the jqGrid own ThemeRoller Css file. For example (Redmond theme):

<link rel="stylesheet" type="text/css" media="screen" href="/themes/redmond/jquery-ui-1.8.2.custom.css" />
<link rel="stylesheet" type="text/css" media="screen" href="/themes/ui.jqgrid.css" />