Why use a Child Theme?

I created a child theme of TwentyTen for BilligaResor:
twentyten-wautom

Here are a few reasons:

If you modify an existing theme and it is updated, your changes will be lost. With a child theme, you can update the parent theme (which might be important for security or functionality) and still keep your changes.
It can speed up development time.
It’s a great way to get started if you are just learning WordPress theme development.

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2014.01.15
Activate this child theme: twentyten-wautom.

IMPORTANT:

style.css

/*
Theme Name: Twenty Ten wautom
…….
Text Domain: twentyten
Template: twentyten

*/

!!! you must add this:
Template: twentyten

IF NOT, you will get error:

Broken Themes

The following themes are installed but incomplete. Themes must have a stylesheet and a template.
Name Description