Modify Web.config

- Open web.config, in configuration section:

          <configSections>
              <section name="ExtAspNet" type="ExtAspNet.ConfigSection, ExtAspNet"/>
          </configSections>

          <!-- Avaiable configurations (Here list the default values): Language="zh_CN" AjaxTimeout="60" EnableAjax="true" Theme="blue" FormMessageTarget="qtip" FormOffsetRight="20" FormLabelWidth="100" FormLabelSeparator="：" IconBasePath="~/icon" EnableAjaxLoading="true" AjaxLoadingType="default" CustomTheme="" CustomThemeBasePath="~/theme" -->
          <ExtAspNet EnableBigFont="true" DebugMode="false" />

  Parameters in ExtAspNet config section:
  - Theme: Control theme, with three built-in themes (blue/gray/access, Default value: blue)
  - Language: Control language (en/zh_CN/zh_TW/..., Default value: zh_CN)
  - FormMessageTarget: The display target of form field error tips (side/qtip, Default value: side)
  - FormOffsetRight: The distance between form field content and right border (Default value: 20px)
  - FormLabelWidth: Form label width (Default value: 100px)
  - FormLabelSeparator: Separator of form field label and field content (Default value: "：")
  - EnableAjax: Enable AJAX (Default value: true)
  - AjaxTimeout: AJAX timeout (Unit: second, Default value: 60s)
  - EnableBigFont: Enable big font. If enabled this property, all 11px font will changed to 12px (Default value: false)
  - DebugMode: Enable debug mode. If enabled this property, the output JavaScript code will be formatted for debug purpose (Default value: false)
  - EnableAjaxLoading: Enable Ajax loading tip (Default value: true)
  - AjaxLoadingType: Ajax loading type. Default to show a yellow tip on top of page, you can modify this property to use extjs loading tip (default/mask, Default value: default)
- In system.web section:

          <pages>
            <controls>
              <add assembly="ExtAspNet" namespace="ExtAspNet" tagPrefix="ext"/>
            </controls>
          </pages>

          <httpModules>
            <add name="ExtAspNetScriptModule" type="ExtAspNet.ScriptModule, ExtAspNet"/>
          </httpModules>

          <httpHandlers>
              <add verb="GET" path="res.axd" type="ExtAspNet.ResourceHandler, ExtAspNet"/>
          </httpHandlers>

- Done.

Attention Please:
Project base on .Net 4.0, you must add two properties controlRenderingCompatibilityVersion and clientIDMode to <page> tag.

        <pages controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID">
            <controls>
            <add assembly="ExtAspNet" namespace="ExtAspNet" tagPrefix="ext" />
            </controls>
        </pages>

Also be careful of Newtonsoft.Json.dll version:
ExtAspNet.dll only has one version for .Net2.0, which can be used in project based on .Net2.0, 3.5, 4.0.
However Newtonsoft.Json.dll has separate versions for different .Net versions.
If your project is based on .Net2.0, please reference the file json.net\Net20\Newtonsoft.Json.dll; If your project is based on .Net4.0, you should reference the file json.net\Net40\Newtonsoft.Json.dll.