What kind of error Invoke-WebRequest produces then it's always end up in output?

I’m trying to figure out what exactly Invoke-WebRequest cmdlet doing differently then other cmdlets as far as error output is concerned. If you execute it with non-existing URL then you end up with errors being put out into output stream. I assume if I use -ErrorAccount parameter to Silent then it will not show up in stream but it does not work. The same happens if I redirect output to Out-Null. Errors are still end up in a stream. What exactly is happening behind the scenes here?

Invoke-WebRequest http://www.cnn.com/nonexist.htm -ErrorAction Silent | out-null

Hey GS,
Difference is that invoke-webrequest is throwing a Terminating Error

You can see this by using Start-Transcript and Stop-Transcript

    Invoke-WebRequest http://www.cnn.com/nonexist.htm
    Get-Content c:\asdfas.fasdf

If you need to catch a terminating error, use try{} catch{}

    try{Invoke-WebRequest http://www.cnn.com/nonexist.htm}
    catch{"Invoke-WebReqeust returned a terminating error"}