How to add Custom Search Engines to Search Bar

Question

In the past I managed to add a 'Custom Search Engine' to Firefox's 'Search Bar' (Windows Version) by just right-clicking that site's own 'search bar' and choosing 'Add to search bar'. I had no third party plugin installed to do this. It was provided by Firefox itself.
Or am I mixing up this feature with Google's 'Add Custom Search Button' ?
Anyhow, is there a way to add a 'Custom Search Engine' to Firefox's 'Search Bar' from any website, WITHOUT having to:
* install an add-on (like: Add to Search Bar 2.0)
* acquire search engines on 'mycroft.mozdev.org'
* acquire search engines from 'Manage/Add Search Engines' from the drop-down menu in the search bar ?
Thanks!

Answer 1

Just made this [http://www.tobtu.com/customsearch.php custom search creator] to do this since I couldn't find one either.
Although I wouldn't trust a stranger so here's the hard way:
Install Apache (lamp/wamp whatever) or get free web hosting from some site.
blah.html:
<a onclick="window.external.AddSearchProvider('http://localhost/blah.xml');">blah</a>
blah.xml:<br />
<br />
<pre><nowiki><?xml version="1.0" encoding="UTF-8"?>
<OpenSearchDescription xmlns="http://a9.com/-/spec/opensearch/1.1/">
<ShortName>Blah</ShortName>
<Description>Blah blah</Description>
<Image width="16" height="16">data:image/png;base64,BlahBlahBase64AndUriEncoded%2B%2F</Image>
<Image width="16" height="16">http://blah/OrJustAUrl.png</Image>
<Url type="text/html" method="get" template="https://blah/?blah={searchTerms}"/>
</OpenSearchDescription></nowiki></pre>
Now go to http://localhost/blah.html and click the link.