We can add our custom tags in web config. I got solution from internet with below example. Please check below:

				
<configuration>
	    <configSections>
        	<sectionGroup name="Test">
        	    <section name="pageStyle" type="Xpode.MyName, MyStyle" />
	        </sectionGroup>
	    </configSections>        
	    <devhood>
        	<pageStyle backColour="navy" />
	    </devhood>
</configuration>

namespace Xpode
{
    internal class MyName : IConfigurationSectionHandler
    {
        public virtual object Create(Object parent, Object context, XmlNode node)
        {
            MyStyle config = new MyStyle((PageStyle)parent);
            config.LoadValuesFromConfigurationXml(node);
            return config;
        }
    }

    public class MyStyle
    {
        string _backColour;

        internal MyStyle(PageStyle parent)
        {
            if (parent != null)
                _backColour = parent._backColour;
        }

        internal void LoadValuesFromConfigurationXml(XmlNode node)
        {
            XmlAttributeCollection attribCol = node.Attributes;
            _backColour = attribCol["backColour"].Value;
        }

        public string BackColour
        {
            get
            {
                return _backColour;
            }
        }
    }
}