Magento system.xml and 404 error when trying to access the configuration panel

Hi I think there is something wrong with the action tag in config.xml.

<action>adminhtml/tempest_main</action>

If I am not mistaken this would refer the the adminhtml module found in app/code/core/Mage/Adminhtml.

What is the name of your module and what do you have in your controllers folder.

I believe that the first bit of the action should be the name of your controller and then the path your admin controller and action

The action tag is built in the following manner.

<action>matrixrate/adminhtml_index/index</action>
       |--module--|--controller---|-action-|

HTH

If it's the 404 in the Admin Console chrome, then your problem is a missing ACL role. Read this article on how to set one up. (self link)

Also, after setting up your ACL role, you'll need to clear out your Magento sessions. Magento caches specific roles in the session, and new sessions won't be automatically added to the cache of users with the super user role.

Give acl permission in your config.xml.

<adminhtml>
        <acl>
            <resources>
                <all>
                    <title>Allow Everything</title>
                </all>
                <admin>
                    <children>
                        <system>
                            <children>
                                <config>
                                    <children>
                                        <tab_name>
                                            <title>Module - All</title>
                                        </tab_name>
                                    </children>
                                </config>
                            </children>
                        </system>
                    </children>
                </admin>
            </resources>
        </acl>
    </adminhtml>

Flush the cache, logout and again login.