Grammar does not equal spelling.
In linguistics, grammar is the set of structural rules that governs the composition of clauses, phrases, and words in any given natural language. The term refers also to the study of such rules, and this field includes morphology, syntax, and phonology, often complemented by phonetics, semantics, and pragmatics. Linguists do not normally use the term to refer to orthographical rules, although usage books and style guides that call themselves grammars may also refer to spelling and punctuation.
Nice direct quote from Wikipedia. Try using reliable sources like dictionary.com or merriam-webster.
Wikipedia is credible, are you people that dumb? Everytime I hear that I just link people to the bottom of the page with all of the citations. Here is the Purdue OWL page listing spelling under grammar:
http://owl.english.purdue.edu/owl/section/1/5/Grammar from merriam webster
1
a : the study of the classes of words, their inflections, and their functions and relations in the sentence
b : a study of what is to be preferred and what avoided in inflection and syntax
2
a : the characteristic system of inflections and syntax of a language
b : a system of rules that defines the grammatical structure of a language
3
a : a grammar textbook
b : speech or writing evaluated according to its conformity to grammatical rules
4
: the principles or rules of an art, science, or technique <a grammar of the theater>; also : a set of such principles or rules Grammar of the English language includes spelling. Fuck right off with your shit.