Archives - Default archive template
Even though there is a link at the bottom of your archive template page claiming to lead to the "default archive template", there is no such thing (thus the 404 error when you click the link). There are two styles of archive links: a separate archive index page (you click a link in your main page, and a separate page opens with links to your archive files), or links included in the main page with javascript. For a separate archive index page, your archive template needs to contain the html for an entire page, while for included links it will only contain the code to create the links.
Separate archive index page
Link to your archives in your main template:
<a href="<$BlogArchiveFileName$>">Archives</a>
Then, to create your archive template, copy your main template, paste it into your archive template (replacing anything that is there now), and replace the <Blogger> to </Blogger> section with:
<Blogger>
<a href="<$BlogArchiveLink$>"><$BlogArchiveName$></a><br>
</Blogger>
Links included in main page
In your main page, where you want the links to appear:
Archives<br>
<script type="text/javascript" src="<$BlogArchiveFileName$>"></script>
In your archive template, delete every single character that is there now, and include only:
<Blogger>
In either case, if your blog is not on Blog*Spot, and if your archives are not in the same directory as your main page, you will need to include a path in front of <$BlogArchiveFileName$> in your main template, and for included links, in front of <$BlogArchiveLink$> in your archive template. The path can be either an absolute path (starting with http://www.domain.com) or a server-rooted path (starting with a / and listing all the directories from the server's root directory, e.g. /philringnalda/blog/archives/<$BlogArchiveFileName$>), but it has to work in both your main directory and your archive directory.
document.write("<a href='<$BlogArchiveLink$>'><$BlogArchiveName$></a><br>");
</Blogger>
if (location.href.indexOf("archive") != -1) {
document.write("<a href='<$BlogURL$>'>current</a>")
}