Example showing how to get the X&Y from a mouse click and place a DIV at that location

dynamicDivXY.js

var dynamicDivIDs = new Array();

function random() {
    return Math.floor(Math.random() * 10000) + 1;
}

function newDivID() {
    var newIDPrefix = 'dynamicDiv';
    var newID  = newIDPrefix + random();

    for(i=0; i<dynamicDivIDs.length;i++) {
        if(dynamicDivIDs[i] == newID) {
            i=0;
            newID = newIDPrefix + random();
        }
    }

    dynamicDivIDs.push(newID);

    return newID;
}

function createDiv(event) {
    placeDiv(event.clientX, event.clientY);
}

function placeDiv(x_pos, y_pos) {
    var newID = newDivID();

    var d = document.createElement('div');
    d.id = newID;
    d.style.position = "absolute";
    d.style.left = x_pos+'px';
    d.style.top = y_pos+'px';
    d.innerHTML = "ID = " + newID;

    document.getElementsByTagName('body')[0].appendChild(d);
}

document.addEventListener("click", createDiv);