In order to detect multiple keys being held down, use the keydown and keyup events.

var keys = {};

$(document).keydown(function (e) {
    keys[e.which] = true;
});

$(document).keyup(function (e) {
    delete keys[e.which];
});

I've put together a demo here: http://jsfiddle.net/gFcuU/. It's kind of fun, though I noticed my keyboard is only able to detect at most 6 keys.

It depends. For "normal" keys, that means Non- Shift, Ctrl, ALT, (CMD), the answer is no, the event handler will catch/fire in a queue, one after another.

For the modifier keys I mentioned above, there is a property on the event object.

Example:

$(document).bind('keypress', function(event) {
    if( event.which === 65 && event.shiftKey ) {
        alert('you pressed SHIFT+A');
    }
});

Jsfiddle demo.

Other propertys are:

• event.ctrlKey
• event.altKey
• event.metaKey

If you just want to fire a handler when several keys are pressed in series, try something like:

jQuery.multipress = function (keys, handler) {
    'use strict';

    if (keys.length === 0) {
        return;
    }

    var down = {};
    jQuery(document).keydown(function (event) {
        down[event.keyCode] = true;
    }).keyup(function (event) {
        // Copy keys array, build array of pressed keys
        var remaining = keys.slice(0),
            pressed = Object.keys(down).map(function (num) { return parseInt(num, 10); }),
            indexOfKey;
        // Remove pressedKeys from remainingKeys
        jQuery.each(pressed, function (i, key) {
            if (down[key] === true) {
                down[key] = false;
                indexOfKey = remaining.indexOf(key);
                if (indexOfKey > -1) {
                    remaining.splice(indexOfKey, 1);
                }
            }
        });
        // If we hit all the keys, fire off handler
        if (remaining.length === 0) {
            handler(event);
        }
    });
};

For instance, to fire on s-t,

jQuery.multipress([83, 84], function () { alert('You pressed s-t'); })