--rootpath: effect -> affect typo.

Author: seven-phases-max

content/usage/command-line-usage.md

@@ -247,7 +247,7 @@ lessc -rp=resources/
 lessc --rootpath=resources/
 ```
 
-Allows you to add a path to every generated import and url in your css. This does not effect less import statements that are processed, just ones that are left in the output css.
+Allows you to add a path to every generated import and url in your css. This does not affect less import statements that are processed, just ones that are left in the output css.
 
 For instance, if all the images the css use are in a folder called resources, you can use this option to add this on to the URL's and then have the name of that folder configurable.