You should put the following code in web.config file:

<configuration>
<system.webServer>
<defaultDocument>
<files>
<add value="index.ashx" />
</files>
</defaultDocument>
</system.webServer>
</configuration>
Please write code to redirect your required page in the page load of  (index.aspx) file. Note that you have to choose correct path of your  start up page if your start up page is located in sub folder of your  project.

protected void Page_Load(object sender, EventArgs e)
{
Response.Redirect("FormBusiness/KPIPerson.aspx");
}
After doing in the above, you can get your project’s start up page as KPIPerson.aspx.

Reference: http://stackoverflow.com/questions/1022949/change-default-startup-page-asp-net-windows-hosted-godaddy