I see this word quite often, and can't find it in the dictionary or wakan. Here's a sentence that uses it.
いったことがありません!
ittako to ga arimasen!
From this I figure it's a negative expression of something, but what is ittako?
And following this I have another sentence:
いってみたぁ~~~ぃ
ittemi taxa
(Did I get that right?)
What does this mean, and is it informal when used like this?