Remapping URLs in your application's web configuration file : URL « Page Lifecycle « ASP.NET Tutorial

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Remap the Home.aspx page to the Default.aspx page.

File: Web.Config

<configuration>
<system.web>
  <urlMappings>
    <add
      url="~/Home.aspx"
      mappedUrl="~/Default.aspx"/>
  </urlMappings>
</system.web>
</configuration>

The tilde character (~) represents the current application root. 
A forward slash (/) at the start of a URL represents the website root.