Google's reasonably good at picking out your spelling mistakes, especially for common terms, but sometimes this leads to it showing you corrected results that aren't exactly correct. It's amending that today, rolling out a 'Verbatim' search function. Verbatim search (nothing to do with flicking through a pile of old 5.25 floppies for the old-timers amongst us) is exactly what it says on the tin; if you select it from Google's advanced search page, it'll use exactly what you typed in as its reference terms, even if you misspell words. I'd love to say that I've tested it, but as yet, it doesn't seem to have rolled out in Australia.
On the official Google Search Blog, Corin Anderson, Google's Principal Search Engineer writes that
We’ve received a lot of requests for a more deliberate way to tell Google to search using your exact terms. We’ve been listening, and starting today you’ll be able to do just that through verbatim search. With the verbatim tool on, we’ll use the literal words you entered without making normal improvements such as making automatic spelling corrections personalizing your search by using information such as sites you’ve visited before including synonyms of your search terms (matching “car” when you search [automotive]) finding results that match similar terms to those in your query (finding results related to “floral delivery” when you search [flower shops]) searching for words with the same stem like “running” when you’ve typed [run] making some of your terms optional, like “circa” in [the scarecrow circa 1963]
Which means, amongst other things, that if you do search with Verbatim on, you'll probably have to sift through a lot more garbage to get the results you want. [Google Search Blog]