Adding CSV file from a URL is not showing columns

[SébastienKoller]

In ArcGIS Online, when adding a csv file from a URL (Add Layer from Web), the system doesn't recognize the columns, it only shows _html_.  But my csv file contains the following columns: FID, ISO-3166 alpha-2, NS deployed

[ChrisWhitmore]

Hi Sébastien - one thing to check is the response from the server providing the csv. The headers that are returned  when the request is made from the map viewer may be causing the CSV to be interpreted as something other than text (which would potentially cause parsing to fail, etc). 

You can check this out using a browser's developer tools (Chrome has a great set). Esri technical support can assist as well. In the response headers from the request for the CSV, you should see content-type as a property. This is an example from the USGS for their recent earthquakes feed: