We are seeing same error in two of our latest projects made in 7.3.1

The CMS will get logged out and the IIS login popup displays.

Hi Anz

Had another look at this, found answer on

http://stackoverflow.com/questions/19286564/umbraco-6-home-errors-out-on-appharbor

Have changed my global.asax file to

<%@ Application Codebehind="Global.asax.cs" Inherits="Umbraco.Web.UmbracoApplication" Language="C#" %>

As yet it has not happened again, ok the WARN ....is 404 is still there but it has not restarted IIS.

Hope this helps

Gary

Using 7.3.1 - I am getting the exact same error in UmbracoTraceLog.txt file:

 2016-02-15 10:54:18,379 [P3868/D2/T3] WARN  Umbraco.Web.UmbracoModule - Status code is 404 yet TrySkipIisCustomErrors is false - IIS will take over.

My Global.asax file looks like this:

<%@ Application Codebehind="Global.asax.cs" Inherits="Umbraco.Web.UmbracoApplication" Language="C#" %>

I cannot trace where the 404 is coming from (have checked IIS W3C log).

Have you found a fix / does the problem still occur on your end?

• a side effect for me is that eventually the entire side will produce a 404 status on all pages rendering the site dead = lost customers. Only way to solve it is to restart Application Pool but the problem resurfaces from time to time. Another user had a similar problem described here: Published pages returning 404 - however the suggested solution won't fix it for me.

Hoping for some help as I have no more troubleshooting ideas left.

We are running 7.4.1 and have just seen this problem. 100s of 404 errors in the logs for a few hours then it resolved itself.

What is the solution?

Status code is 404 yet TrySkipIisCustomErrors is false - IIS will take over.

I saw this error where we were blocking the /umbarco URL on the production server using a rewrite rule. We ended up adding )(?!/RestServices/)(?!/ping.aspx) to the end.

<rule name="Restrict access" stopProcessing="true"> 
  <match url="umbraco(?!/Surface/)(?!/Api/)(?!/api/)(?!/webservices/)(?!/RestServices/)(?!/ping.aspx)" />
  <conditions logicalGrouping="MatchAny" trackAllCaptures="false"> 
    <add input="{HTTP_HOST}" matchType="Pattern" pattern="^management.host.com$" 
     ignoreCase="true" negate="true" /> 
  </conditions> 
<action type="Redirect" url="/not-found" appendQueryString="false" /> 

We are having this problem in v7.4.2 on a new site. Literally hundreds and hundreds of them.

We have a couple of content finders in the site and we have also inherited from Umbraco.Web.UmbracoApplication in our global.cs file.

Any pointers help would be appreciated.

Anyone found a solution for this?

We have 2 sites that are getting the warning

WARN Umbraco.Web.UmbracoModule - Status code is 404 yet TrySkipIisCustomErrors is false - IIS will take over.

1) is running 7.3.3 and are getting the warning every 2 seconds.

2) is running 7.3.5 and are getting the warning every 1 min and 30 seconds.

both are running as https.

I have solved it by setting trySkipIisCustomErrors to true in /Config/umbracoSettings.config as well.

My project's Umbraco version is 7.4.3 assembly: 1.0.5948.18141

According to the information provided in current umbraco settings file (my version is already 7.15.1):

@trySkipIisCustomErrors
        Tries to skip IIS custom errors.
        Starting with IIS 7.5, this must be set to true for Umbraco 404 pages to show. Else, IIS will take
        over and render its built-in error page. See MS doc for HttpResponseBase.TrySkipIisCustomErrors.
        The default value is false, for backward compatibility reasons, which means that IIS _will_ take
        over, and _prevent_ Umbraco 404 pages to show.

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