Spelling errors are like polio.
They should have been completely wiped out by spellchecking software, just as polio was eradicated by vaccines. But sadly, out there in the jungles of bad writing, you can still find atrocious cases of misspelled words.
Spelling mistakes are a sign of a shoddy and lazy mind. They signal a writer's utter disregard for his audience. And only the most derisive author lacks the decency to spend twenty seconds on a quick spellcheck before putting work out in front of readers.
Even basic blogging sites like Blogger have built-in spellcheckers. Use them. Don't maul your credibility.