To set up custom error page in Asp.net.simply you have to just add a custom error code in
web.config file for aspx pages.and for Non aspx pages like html,php,jsp or only strings after url, you have to add httperrors code to web.config file.
>> Add below codes in <configuration> Tag in web.config
For Aspx Pages
<system.web>
<customErrors defaultRedirect="404.aspx" mode="On">
<error redirect="404.aspx" statusCode="404" />
</customErrors>
</system.web>
For Non-Aspx pages
<system.webServer>
<httpErrors errorMode="Custom">
<remove statusCode="404" subStatusCode="-1" />
<error responseMode="Redirect" statusCode="404" prefixLanguageFilePath=""
path="404.aspx" />
</httpErrors>
</system.webServer>
you can design your 404 page using these links
http://www.smashingmagazine.com/2009/01/29/404-error-pages-one-more-time/
web.config file for aspx pages.and for Non aspx pages like html,php,jsp or only strings after url, you have to add httperrors code to web.config file.
>> Add below codes in <configuration> Tag in web.config
For Aspx Pages
<system.web>
<customErrors defaultRedirect="404.aspx" mode="On">
<error redirect="404.aspx" statusCode="404" />
</customErrors>
</system.web>
For Non-Aspx pages
<system.webServer>
<httpErrors errorMode="Custom">
<remove statusCode="404" subStatusCode="-1" />
<error responseMode="Redirect" statusCode="404" prefixLanguageFilePath=""
path="404.aspx" />
</httpErrors>
</system.webServer>
you can design your 404 page using these links
http://www.smashingmagazine.com/2009/01/29/404-error-pages-one-more-time/