update README.md.

README.md

@@ -20,3 +20,11 @@ Here are some guidelines of the usage of LESS :
 * You can use the latest released version, i.e. the latest syntax.
 * You don't need to care the size of generated CSS. We can anyway use optimiser to grouping similar rules.
 * If you are not sure which you should choose between 'mixin' and 'extend', always use 'mixin'.
+
+JavaScript
+----------
+
+Here are some guidelines of the usage of JavaScript :
+
+* Never try tricky things with JavaScript in Form appearance, that may easily break browser compatibility.
+* JQuery is available. Feel free to use it as much as possible for better readability and maintainability of the code.