website "connection timed out" is it an internal error ??

Hi i'm getting lot of connection timed out for a website which has been configured for monitoring. the connection timed out has a blank response code. i'm bit confused does the connection timed out needs to be alerted is it more of a network issue or is it an internal client side error because server issue will give you response code > 500 . as there is no response code in this event. how should it be interpreted. My client is trying to understand what exactly is the response code for connection timed out if we highlight this could it be a false positive alert any insights/suggestions would be a great help