This is an old trick, gang... veterans such as myself were doing this to people 10 years ago at Trollvalhalla.
Elementary stuff
You go through an old PM, use the "save as" function on your browser to download the webpage currently displayed to you. You then right click on the .html file to edit (preferably with Notepad++) and do a search for the body of the message contained within, you change that to whatever you want and then save the file. Next you open the .html file in a browser of your choice and take a screen print of what is displayed back to you. You then use Paint to crop out the URL bar which will now read File:\\xxxxxx.html instead of
http://thirfuckingfail.com and you're all set.
notice how the image does not have a url bar?
Sadly, this dumbfuck did not know how to locate the exact placement of the timestamp to modify that as well, hence the September 20
2017 date,