please add below mentioned code in your web.confilg file. it will create startup page run order for your application.
<system.webServer>
<defaultDocument>
<files>
<clear/>
<add value="Default.aspx"/>
<add value="login.aspx"/>
<add value="Default.htm"/>
<add value="Default.asp"/>
<add value="index.htm"/>
<add value="index.html"/>
<add value="iisstart.htm"/>
</files>
</defaultDocument>
</system.webServer