How do you stop the 999 Yahoo Error?

try not putting links or website references with your answers, and see if it will stop. some websites might be banned for use from yahoo answers....or at least just try "scamming" this website by writing out urls like w w w dot...etc etc

if it still occurs, try signing out, exit your internet window, restart the computer, come back on yahoo answers, and sign in. i had a weird bug too. i had to sign in everytime i wanted to post a question or answer...and that worked for me...but of course the problem you have is different

you could also try to just create a different account....but i have no idea, and having multiple accounts is restricted...

if you are answering someone with any link inside your question....then be sure that link has banned by yahoo......yahoo want to promote their own products here.......find an alternate link and paste............or try to answer same question without that link that will fix your problem.

EDIT

and also this problem is not forever...after few days you will again able to paste that link again...so dont worry about that.