Observer not firing - adminhtml_block_html_before

Question

I've been trying to develop a new module which will modify the admin html pages of a magento control panel but I'm having difficulty getting it to work. To debug I've rolled the module back to some really simple code to just write to the system.log file when the product edit page loads... and this still isnt working so I think I've got a problem with the observer actually firing. Can you see any problems?

app/etc/modules/tww_RemoveProductTabs.xml

<?xml version="1.0"?>
<config>
    <modules>
        <tww_RemoveProductTabs>
            <active>true</active>
            <codePool>local</codePool>
        </tww_RemoveProductTabs>
    </modules>
</config>

app/code/local/tww/RemoveProductTabs/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <tww_RemoveProductTabs>
            <version>0.1.0</version>
        </tww_RemoveProductTabs>
    </modules>
    <global>
        <models>
            <tww_RemoveProductTabs>
                <class>tww_RemoveProductTabs_Model</class>
            </tww_RemoveProductTabs>
        </models>
        <events>
            <adminhtml_block_html_before>
                <observers>
                    <tww_RemoveProductTabs>
                        <class>tww_RemoveProductTabs/observer</class>
                        <method>removeTabs</method>
                        <type>singleton</type>
                    </tww_RemoveProductTabs>
                </observers>
            </adminhtml_block_html_before>
        </events>
    </global>
</config>

app/code/local/tww/RemoveProductTabs/Model/Observer.php

<?php
    class tww_RemoveProductTabs_Model_Observer
    {
        public function removeTabs(Varien_Event_Observer $observer)
        {
            Mage::log("Observer triggered");
        }
    }
?>

Answer 1

You have to properly close the tww_RemoveProductTabs node:

<tww_RemoveProductTabs>
    <class>tww_RemoveProductTabs/observer</class>
    <method>removeTabs</method>
    <type>singleton</type>
</tww_RemoveProductTabs>  // you have to properly close `tww_RemoveProductTabs`