FFS!  

These are just a few of the 74! abbreviations listed in a glossary on a discussion forum site:

• FFS for f**k's sake
• FWIW for what it's worth
• FYI for your information
• HTH hope this helps
• IIRC if I remember correctly
• IKWYM I know what you mean
• IME in my experience
• IMHO in my humble opinion
• IMO in my opinion
• IYKWIM if you know what I mean
• IYSWIM if you see what I mean
• LMP last menstrual period
• LOL laugh out loud

( . . . . for the sake of full disclosure, the discussion forum is for parents and people trying to become parents—still, that second-to-last item took me a little by surprise.)