I see a lot [A LOT] of grammar mistakes made by users and admins alike on this site, but one in paticular makes me mad; the missuse of apostrophes.
Now, I'm no English major, but I, for the most part, know the basic rules of the English language. However, if you ARE an English major and you spot any mistakes, feel free to correct me.
Plural forms of words: When you are using the plural form of a word, don't use an apostraphe. M'kay?
"Those pencils belong to John."
Possessive: When you are using the posessive form of a word, there are 2 rules;
1- if the word ends in anything other than an S, add " 's ".
2- if the word ends in an S, just add an apostrophe.
1- "That is John's pencil." 2- "That is Thomas' pencil."
Contraction [combining two words like "are not" to make "aren't"]: When using a contraction, the apostrophe takes the place of letter(s) taken out of the word(s).
are + not = aren't [replaces the O.]
I'm no English major, but I would make a correction concerning words ending in the letter 's'.
For possesives:
1) If the word is singular, you still add apostrophe-s.
2) If the word is plural, just an apostrophe is added.
Never adding apostrophe-s to something already ending in 's' is a common mistake made in newspapers and magazines. (There are some name exceptions like "Jesus" and "Zeus"