If you only have access to HTML, CSS and JavaScript and not to some server-side technology, then you will need a JavaScript AIML interpreter.
A quick search turns up the following:
AIML Interpreter written in node.js
AIMLInterpreter is a module that allows you to parse AIML files and to find the correct answer to a given message.
aiml-high written in node.js. Built on aimlinterpreter.
aiml-high is a module that allows you to parse AIML files and to find the correct answer to a given message.
Surly2
a half-complete node.js AIML interpreter with a bad attitude.
Surly2 is a remake from the ground up of Surly using Node 5 and using as much asynchronicity as possible.
burly
Burly is a fork of Surly2