A boxing website pun is:
   
Q: Have you seen the boxing website?
A: Yes, it really knocked me out!
 
The boxing joke has been cited in print since at least 2001.
 
     
Scatty—Internet Jokes (March 9, 2001)
Have you seen the boxing website?
Yes, it really knocked me out!
   
Google Books
Super Goofy Jokes
By Jacqueline Horsfall
New York, NY: Sterling Publishing Company, Inc.
2004
Pg. 79:
Have you seen the boxing website?
It knocked me out!
 
Yahoo! Answers (April 13, 2008)
Its kids time folks are these funny?
Have you seen the baked bean website?
I’ve only just got wind of it.
 
Have you seen the boxing website?
Yes, it really knocked me out!
 
XciteFun.net
STUPEFIED - Have you ever seen?
Post by suchitra » Nov 21, 2008
Have you seen the boxing website?
Yes, it really knocked me out.
       
Twitter
❤️ FizzyDuck ❤️
@FizzyDuck
Have you seen the Boxing website? It really knocked me out!
11:33 AM - 29 Jun 2009
   
Google Books
The Mammoth Book of Really Silly Jokes:
Humour for the whole family
Edited by Geoff Tibballs
London, UK: Constable & Robinson Ltd
2011
Pg. ?:
Have you seen the boxing website?
Yes, it really knocked me out
 
Twitter
Mervyn Trimble
@Murv_IHOW
Have you seen the boxing website?
Yes,  it really knocked me out. 
Boom boom #ihow
6:13 PM - 19 Jan 2011
 
Twitter
k80
@katie__raabe
Have you seen the new boxing website? It really knocked me out!😂😂😂😂👌👌👌👌
12:35 AM - 15 Dec 2013