The Oxford English Corpus has found that "dozens of traditional phrases are now more commonly misspelled than rendered correctly in written English [on the internet]." Looking through the list, I find to my shame I am guilty of some of these infractions myself.
But I remain philosophical about it, as English is a living language that will keep evolving and changing for many decades to come. I only really rankle at manglings of English that don't make sense, like the greengrocer's apostrophe. I'm seeing more and more incorrect English creep into newspapers (who needs proofreaders when you have computers?) and while it annoys me it's important that I remind myself that