Is there somewhere google published the official blogger template language specifications? I read this question and it provided a lot of useful information, but it didn't provide me with help on a particular tag I'm looking for (the variable tag).
While I haven't been able to find an official language specification, I have found a blog called bloggeD written by Bhavya Jain. Starting here:
http://thoughtsomething.blogspot.com/2009/01/understanding-blogger-template-1.html
Jain covers
These blog entries complement the blogger documentation -- Blogger › Help articles › Customize Your Blog › Layouts › Advanced Use, where the most relevant sections contain "Tags" in the title -- with more information (how "expr" works for examples) and more code samples.
The variable tag that you're referring to doesn't appear to be a tag as such. It's a string that you put within the CSS comment (inside your b:skin tag) so that you only have to define colors (and such) once:
<b:skin>
<style type='text/css'>
/*
* Variable definitions:
* <Variable name='bgcolor' description='Page Background Color'
type='color' default='#fff'/>
*/
body {
background: $bgcolor;
margin: 0;
padding: 40px 20px;
}
</style>
</b:skin>
This sample is copied and pasted from Fonts and Colors Tags for Layouts. You can find it on the blogger help page I linked to above. I'd link to it again, but alas I am not cool enough.