This is a template that will cause a Navigation bar to be presented at the bottom of your browser (this is the prefered location, given that aligning to the top by setting valign to any nonempty value will set the Navbar to appear over your first line of text). It will remain in fixed location, despite how your scrollbar scrolls, and will be at the bottom or first line browser-independent. It is useful for common links (much like the bar at the top of the browser) and includes at least a way to get to your User page, your talk page, purge this page, and a link to suggest changes to this template. It also (by default) includes a quick edit link and an email link. It can also contain some extra links of your choice.
By default, the bar is orange, but this can be overriden with bgcolor.
Since you're at the documentation, you can't see the bar. Go to the template.
Usage edit
{{Navbar
|name=<name>
|small=<small>
|bgcolor=<bgcolor>
|valign=<valign>
|noedit=<noedit>
|noemail=<noemail>
|shorten=<shorten>
|links=<links>}}
name-Optional name to override BASEPAGENAME. See known bugs below.
small-If this is any nonempty value, the bar will use normal font (not small font) instead of the usual big font. For large link lists.
bgcolor-Will set the background of the bar to any color but the usual orange.
valign-Not really useful...when this is nonempty, the bar aligns itself at the first line of text on your page (which is close to the middle of the screen; this is more annoying than functional).
noedit-When nonempty, this will inhibit displaying an "edit this page" link. Ideal for protected pages since you would get an "Unauthorized" message anyway.
noemail-When nonempty, this will inhibit the "email me" link. Ideal for users not having an email.
shorten-When nonempty, shortens long links (like "Edit this page" to just "Edit" and "Email me" to "Email"). Useful for users wishing to keep the big formatting but using large link lists.
links-Any extra links you would like to add to the end of the Navbar (after the "Suggest Navbar changes" link).
Known bugs edit
BASEPAGENAME not working for >2 levels edit
The BASEPAGENAME feature works fine for any user page and one subpage beneath that, but any more subpages will cause it to report the root of this page, which isn't a user, so it can't be emailed (home and talk can be accessed though; hence it acts like a "step out").
FIX: A parameter called name has been added (it is optional). When empty, BASEPAGENAME is used. When nonempty, it overrides the BASEPAGENAME ans is used as your username.
It is also suggested to create one user subpage to house your Navbar, then transclude that page, so a change to one param on that page is global.