Which one is correct below,
Many Thanks in advance
Many Thanks In Advance
Exactly. " Its reputation has not risen over the years, and it is still a long way from general acceptance. Use regardless instead."Whilst I agree with you entirely about its usage, while in Madrid recently I was pointed in the direction of this:
Irregardless - Definition and More from the Free Merriam-Webster Dictionary
The final sentence is the important one, of course.