function KeywordsTextBox_KeyPress(sender, eventArgs) {
    if (eventArgs.keyCode == 13) {
        SearchButton_Click();
        return false;
    }
}

function SearchButton_Click(sender, eventArgs) {
    var keywordsTextBox = document.getElementById("KeywordsTextBox");
    if (keywordsTextBox.value == ""
        || keywordsTextBox.value == "Enter Keyword(s)") {
        alert('Please enter a keyword to search for.');
        keywordsTextBox.focus();
        return;
    }
    window.location = '/SearchResults.aspx?QueryExpr=' + keywordsTextBox.value;
}