var searchBox = document.getElementById('SearchForm_SearchForm_Search');
var searchText = searchBox.value;

function clearFormSearchText() {
    if (searchText == 'Search') {
        searchBox.value = '';
    }
    return false;
}

function setFormSearchText() {
    if (searchBox.value == '') {
        searchBox.value = 'Search';
    }
}

searchBox.onclick = clearFormSearchText;
searchBox.onblur = setFormSearchText;