Shortcut key or hot key in website

ALT + A has no ASCII code (but the keyCode is 18), only A has an ASCII code and you will be testing against that one only. However, you will also be testing if the ALT key is also pressed by the user.

I would recommend attaching an event handler to the HTML document (or in a much recommended way, to the body element) and then handle it using JavaScript. So, for that just try this:

$(document).ready(function () {
    $('body').keydown(function () {
        if(window.event.altKey == true && window.event.keyCode == 65) {
            document.getElementById("landing").innerText = "Alt + A pressed.";
        } else {
            document.getElementById("landing").innerText = "Alt + A combination not made.";
        }
    });
});

This can also be tested at, Edit fiddle - JSFiddle[^]. You can now also add more combinations for the keys as per they are needed.

For more: KeyboardEvent Value (keyCodes, metaKey, etc) | CSS-Tricks[^]