Which one is correct?

弘法にも筆の誤り

http://blog.goo.ne.jp/i-musashi/e/37d22b...b3535fd201

or

弘法も筆の誤り

http://www.languagerealm.com/japanese/ja...rbs_ko.php


and what is the difference?

I'd trust the native source, not the translation website. That's just me though.

Not to mention in his romanization of 弘法 he wrote "Koukou"

According to Koujien, they're both acceptable.

How can we translate each of them?