1. Log into your Magento Admin panel and navigate to CMS -> Static Blocks

2. Click on Add New Block button:

3. Specify your Block Title and Block Identifier.

4. Remember or copy your Identifier.

5. Select the store view for which you want to add this Static block and alter the Content Field:

6. Using your FPT client or any FileManager, navigate to app\design\fontend\default\themeXXX\template\page\html folder.

7. Open header.phtml file using any text editor.

8. Depending on where exactly you wish to place your Static block, paste the following code:

<?php echo $this->getLayout()->createBlock('cms/block')->setBlockId('custom_block_id')->toHtml() ?>

where custom_block_id is your identifier which you’ve indicated when creating the Static Block:

9. Save this file and upload to the server.

10. Reload your site to see the changes.