Irregardless is considered incorrect in Standard English, but has existed in US English since the 19th or early 20th century, however most Americans consider it wrong to use it.
>>0 That last sentence made me do a spittake.
Just two days ago 'irregardless' was considered a useable word. I read it in the news. I always knew it was wrong but the public uses it so much the word wizards gave in.