triggers

HTML

<select id="user_number" name="user_number" onchange="onProjectChange()">
<option disabled selected>Выберите клиента...</option>
<option value="1">kukueva</option>
<option value="2">petrova</option>
<option value="3">ivanova</option>
</select>

CSS

* { font-family: Tahoma, Geneva, sans-serif; }
ul {
 width: 100px;
 background-color: #EEE;
 border: 1px solid #333;
 cursor: default;
}
ul li {
 margin:1px;
 padding:2px;
 border: 1px solid #333;   
}
textarea {
 display: block;
 width: 500px;
 min-height: 300px;
 padding: 5px;
 color: #e5e517;
 background-color: #010101;
 border: 3px dashed #4d4d4d;
}

JavaScript

function onProjectChange() {
var usrnum = $(this).find('option:selected').attr('value')
//var usrnum = document.getElementById('user_number').value;  
$.ajax({
type: "POST",
url: "http://cv.cskg.ru/inc/btob.php",
data: usrnum: usrnum,
cache: false,
success:
alert (data);
    error: slert (data); 
});

};