Asp.net – error when trying to access working webpage

I have created an asp.net webpage and have uploaded it onto a webserver. However when I try to view the page remotely, I get errors about the customerror tag in the web.config file. The page works locally with no errors or warnings. Also if I upload the page as a .html file, I can view it fine remotely.
I have seen a lot of other people with this error, but the ‘solutions’ just say to change the customErrors tag to ‘Off’, which I have done and does not work, do you know is there an issue with the webserver or what could be the problem here?

Here is the error page:

Server Error in ‘/’ Application.
Runtime Error
Description: An application error occurred on the server. The current custom error >settings for this application prevent the details of the application error from being >viewed remotely (for security reasons). It could, however, be viewed by browsers running >on the local server machine.

Details: To enable the details of this specific error message to be viewable on remote >machines, please create a tag within a “web.config” configuration file >located in the root directory of the current web application. This tag >should then have its “mode” attribute set to “Off”.

<configuration>
    <system.web>
        <customErrors mode="Off"/>
    </system.web>
</configuration>

Notes: The current error page you are seeing can be replaced by a custom error page by >modifying the “defaultRedirect” attribute of the application’s >configuration tag to point to a custom error page URL.

<configuration>
    <system.web>
        <customErrors mode="RemoteOnly" defaultRedirect="mycustompage.htm"/>
    </system.web>
</configuration>

And here is my web.config file:

<?xml version="1.0"?>
<configuration>

  <system.web>
    <customErrors mode="Off"/>
  </system.web>

  <system.web>
    <compilation debug="true"/>
    <authentication mode="None"/>
  </system.web>
</configuration>

Answers:

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Method 1

You should only have one <system.web> in your Web.Config Configuration File.

<?xml version="1.0"?>
<configuration>
  <system.web>
    <customErrors mode="Off"/>
    <compilation debug="true"/>
    <authentication mode="None"/>
  </system.web>
</configuration>

Method 2

None of those solution work for me but i have this in my web.config

<log4net debug="true">

either remove all those or go and read errors logs in your application folderlogs

Method 3

Sometime in the future
Comment out the following code in web.config

 <!--<system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701" />
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=&quot;Web&quot; /optionInfer+" />
    </compilers>
  </system.codedom>-->

update the to the following code.

<system.web>
    <authentication mode="None" />
    <compilation debug="true" targetFramework="4.6.1" />
    <httpRuntime targetFramework="4.6.1" />
    <customErrors mode="Off"/>
    <trust level="Full"/>
  </system.web>

Method 4

For example in my case I accidentaly changed role of some users to incorrect, and my application got error during starting (NullReferenceException). When I fixed it – the app starts fine.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0