Add special warning about the misuse of it's

content-style-guide.md

@@ -367,6 +367,10 @@ The doughnut thief ate Sam’s doughnut.
 The doughnut thief ate Chris’s doughnut.  
 The doughnut thief ate the managers’ doughnuts.  
 
+```{note}
+Note the exception to this rule: the word **it**, which does not use an apostrophe for its possessive, for example: "Our competitor had all its clients' websites hacked."  Agaric avoids contractions so we do not ever use **it's** but rather **it is**.
+```
+
 Apostrophes can also be used to denote that you have dropped some letters from a word, usually to match spoken language— an unofficial contraction. This is fine when quoting or paraphrasing and giving the feel of a statement is important, but do it sparingly.