Hi all,
Here is a tip on how to customize the alert modals (non extjs/Aware IM). The existing alert modals are the ugly JS default ones and with this fix you can customize the style of the modal (Aware IM still populates the right alert text in the alert). See screenshot below for an example. Note: I have limited JS and Aware IM internals etc. knowledge and I don´t think this messes up anything in your application since the actual Aware IM internals code isn´t changed. What´s changed is only the style of the modal. I don´t know this for sure thought so use at own risk and if anyone more knowledgeable (or support) can take a look at this solution and verify that using it is OK, that would be great and appreciated.

Support, the absolute ideal thought would be to either use extjs/Aware IM modals INSTEAD of the existong plan js ones OR integrate an external alert package/library like for example Sweetalert (http://tristanedwards.me/sweetalert).

Source:
http://stackoverflow.com/questions/7853130/how-to-change-the-style-of-alert-box.

Screenshot:

Instructions:
In startup.html (inside head tag) add the following css and js (this should ideally be referenced to in separate files that you link to from your startup.html):

CSS (if you add this in your head tag, the css should be inside <style> tags, if you use an external file it shouldn´t be inside <style> tags). You can customize the CSS how ever you like:

<style>
 #modalContainer {
    background-color:rgba(0, 0, 0, 0.3);
    position:absolute;
    width:100%;
    height:100%;
    top:0px;
    left:0px;
    z-index:9999999;
    background-image:url(tp.png); /* required by MSIE to prevent actions on lower z-index elements */
}

#alertBox {
    position:relative;
    width:300px;
    min-height:100px;
    margin-top:50px;
    border:1px solid #666;
    background-color:#fff;
    background-repeat:no-repeat;
    background-position:20px 30px;
}

#modalContainer > #alertBox {
    position:fixed;
}

#alertBox h1 {
    margin:0;
    font:bold 0.9em verdana,arial;
    background-color:#3073BB;
    color:#FFF;
    border-bottom:1px solid #000;
    padding:2px 0 2px 5px;
}

#alertBox p {
    font:0.7em verdana,arial;
    height:50px;
    padding-left:5px;
    margin-left:55px;
}

#alertBox #closeBtn {
    display:block;
    position:relative;
    margin:5px auto;
    padding:7px;
    border:0 none;
    width:70px;
    font:0.7em verdana,arial;
    text-transform:uppercase;
    text-align:center;
    color:#FFF;
    background-color:#357EBD;
    border-radius: 3px;
    text-decoration:none;
}

/* unrelated styles */

#mContainer {
    position:relative;
    width:600px;
    margin:auto;
    padding:5px;
    border-top:2px solid #000;
    border-bottom:2px solid #000;
    font:0.7em verdana,arial;
}

h1,h2 {
    margin:0;
    padding:4px;
    font:bold 1.5em verdana;
    border-bottom:1px solid #000;
}

code {
    font-size:1.2em;
    color:#069;
}

#credits {
    position:relative;
    margin:25px auto 0px auto;
    width:350px;
    font:0.7em verdana;
    border-top:1px solid #000;
    border-bottom:1px solid #000;
    height:90px;
    padding-top:4px;
}

#credits img {
    float:left;
    margin:5px 10px 5px 0px;
    border:1px solid #000000;
    width:80px;
    height:79px;
}

.important {
    background-color:#F5FCC8;
    padding:2px;
}

code span {
    color:green;
}
</style>

JS (if you add this in your head tag, the js should be inside <script> tags, if you use an external file it shouldn´t be inside <script> tags). Another thing, the ALERT_TITLE and ALERT_BUTTON_TEXT can be changed to whatever you want but make sure you choose a neutral term because these alerts are used extensively throughout applications and contexts:

<script>
var ALERT_TITLE = "Oops!";
var ALERT_BUTTON_TEXT = "Ok";

if(document.getElementById) {
    window.alert = function(txt) {
        createCustomAlert(txt);
    }
}

function createCustomAlert(txt) {
    d = document;

if(d.getElementById("modalContainer")) return;

mObj = d.getElementsByTagName("body")[0].appendChild(d.createElement("div"));
mObj.id = "modalContainer";
mObj.style.height = d.documentElement.scrollHeight + "px";

alertObj = mObj.appendChild(d.createElement("div"));
alertObj.id = "alertBox";
if(d.all && !window.opera) alertObj.style.top = document.documentElement.scrollTop + "px";
alertObj.style.left = (d.documentElement.scrollWidth - alertObj.offsetWidth)/2 + "px";
alertObj.style.visiblity="visible";

h1 = alertObj.appendChild(d.createElement("h1"));
h1.appendChild(d.createTextNode(ALERT_TITLE));

msg = alertObj.appendChild(d.createElement("p"));
//msg.appendChild(d.createTextNode(txt));
msg.innerHTML = txt;

btn = alertObj.appendChild(d.createElement("a"));
btn.id = "closeBtn";
btn.appendChild(d.createTextNode(ALERT_BUTTON_TEXT));
btn.href = "#";
btn.focus();
btn.onclick = function() { removeCustomAlert();return false; }

alertObj.style.display = "block";

}

function removeCustomAlert() {
    document.getElementsByTagName("body")[0].removeChild(document.getElementById("modalContainer"));
}
</script>