lolpops, так?
<!doctype html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
</head>
<body>
<div class="poisk2" align="right">
<u>Процент использования</u><br>
Закладки <input type="number" name="check[0]" id="check-0" min="0" max="100" value="30"> %<br />
Yandex.ru <input type="number" name="check[1]" id="check-1" min="0" max="100" value="40"> %<br />
Google.ru <input type="number" name="check[2]" id="check-2" min="0" max="100" value="20"> %<br />
Nigma.ru <input type="number" name="check[3]" id="check-3" min="0" max="100" value="10"> %<br />
Qip.ru <input type="number" name="check[4]" id="check-4" min="0" max="100" value="0"> %<br />
Go.mail.ru <input type="number" name="check[5]" id="check-5" min="0" max="100" value="0"> %<br />
Rambler.ru <input type="number" name="check[6]" id="check-6" min="0" max="100" value="0"> %<br />
Google.com.ua <input type="number" name="check[7]" id="check-7" min="0" max="100" value="0"> %<br />
Meta.ua <input type="number" name="check[8]" id="check-8" min="0" max="100" value="0"> %<br />
Yandex.ua <input type="number" name="check[9]" id="check-9" min="0" max="100" value="0"> %<br />
Bigmir.net <input type="number" name="check[10]" id="check-10" min="0" max="100" value="0"> %<br />
Bing.com<input type="number" name="check[11]" id="check-11" min="0" max="100" value="0"> %<br />
Yandex.com <input type="number" name="check[12]" id="check-12" min="0" max="100" value="0"> %<br />
</div>
<script>
var wrap = document.querySelector('.poisk2'),
inpElems = wrap.querySelectorAll('input[type=number]');
wrap.onchange = function(e) {
var target = e.target;
if (target.tagName.toLowerCase() != 'input') return;
var result = [].reduce.call(inpElems, function(current, next) {
return (+current.value || +current) + +next.value;
});
if (result <= 100) {
target.style.background = 'red';
}
};
</script>
</body>
</html>