Always spell check your work. I am saying this to you as much as I am to myself. In fact, I probably have spelling errors because I haven't run a spellcheck on any of these blog entries.
Modern-day word processing software underlines spelling errors, so why run a separate spellcheck? In my experience, they don't catch everything, so inevitably your writing will contain spelling errors.
Despite the fact that you have spent untold hours crafting your best work, even the most forgiving readers will become exasperated with spelling errors and may begin to unfairly associate your spelling issues with ingrained character flaws.