IIS 7.5 , 2008rc2, classic asp, 500 error msg:
The page cannot be displayed because an internal server error has occurred.
I nee
If you run the browser in the server and test your url of the project with the local ip you have received all errors of that project without a generally error page(for example 500 error page).
In web.config under
<system.webServer>
replace (or add) the line
<httpErrors errorMode="Detailed"></httpErrors>
with
<httpErrors existingResponse="PassThrough" errorMode="Detailed"></httpErrors>
This is because by default IIS7 intercepts HTTP status codes such as 4xx and 5xx generated by applications further up the pipeline.
Next, enable "Send Errors to Browser" under the "ASP" section, and under "Error Pages / Edit Feature Settings", select "Detailed errors".
Also, give Write permissions on the website folder to the IIS_IUSRS builtin group.
One thing nobody's mentioned is as a very quick and temporary fix, you can view the error on the localhost of that web server.
After trying Vaclav's and Alex's answer, I still had to disable "Show friendly HTTP error messages" in IE
try setting the value of the "existingResponse" httpErrors attribute to "PassThrough". Mine was set at "Replace" which was causing the YSOD not to display.
<httpErrors errorMode="Detailed" existingResponse="PassThrough">
Fot people who have tried EVERYTHING and just CANNOT get the error details to show, like me, it's a good idea to check the different levels of configuration. I have a config file on Website level and on Application level (inside the website) check both. Also, as it turned out, I had Detailed Errors disabled on the highest node in IIS (just underneath Start Page, it has the name that is the same as the webservers computername). Check the Error Pages there.