Welcome to this blog.
Today we are going to discuss non-default themes in magento. We all knows magento is a powerful eCommerce platform where you can easily build your stores. If you want to work on magento then you need to understand it's file structure. Magento provides different in-build functionalities.

There are two main folders in magento setup

A) app B) skin

app folders included many different sub-folders like code, design, etc, locale

Skin folder contains css, javascript and jquery files to maintain the design/layout of the website

Magento includes in-build themes like default, modern and iphone. If you want to create your own theme then you need to follow the different steps.

A) Themes are stored in package folder. You can check the in-build magento themes in app->design->froendend->default . default is a package folder.

B) You can create your own packages in magento and build your own themes in it.

C) We are going to create a package named FindNerd and create folder for theme inside it and you can give it any name. We are going to create a theme folder with name Mastro.

D) There are few necessary files which needs to be created in theme folder.
app/design/frontend/your_package/your_theme/template/page/1column.phtml
app/design/frontend/your_package/default/template/page/1column.phtml
app/design/frontend/base/default/template/page/1column.phtml

skin/frontend/your_package/your_theme/css/styles.css
skin/frontend/your_package/default/css/styles.css
skin/frontend/base/default/css/styles.css

Kindly copy and paste these folders and files from in-build default theme.

E) Now its time to activate it by adding it in configuration. go to system->configuration in design tab from left side. Kindly write down the package name as well as theme folder names in configuration and now you are ready to use your own theme. You can customize your theme as per requirement.