Svyatik95,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
function change () {
this.value.indexOf(this.defaultValue) && (this.value = this.defaultValue);
}
$(".user_linkedin_1").on("input", change);
});
</script>
</head>
<body>
<input type="text" value="http://youtube.com/" style="width: 500px;" class="user_linkedin_1"><br>
<input type="text" value="http://www.yandex.ru/" style="width: 500px;" class="user_linkedin_1">
</body>
</html>