- You can get there using my_changes addon. Look for examples in the Manuals and the KB.
1. create a folder "index" in: skins/your-skin/customer/addons/my_changes/hooks/
So, from your ftp should look like: skins/your-skin/customer/addons/my_changes/hooks/index
2. In there, create a file "main_content.override.tpl . Should look like:
skins/your-skin/customer/addons/my_changes/hooks/index/main_content.override.tpl
3. Inside the tpl file you can write all the changes will affect the header. How?
Look into the main.tpl file located in skins/your-skin/customer/main.tpl, and on line 8 you'll see
{hook name="index:main_content"}
<div id="header">{include file="top.tpl"}</div>
{/hook}
So the way it works, this hook look into the folder "index" for the file "main_content" to replace the "<div id="header">{include file="top.tpl"}</div> ".
4. copy the file top.tpl into the new main_content.override.tpl so your store will look the same. Don't forget to write the <div id="header"> at the begining and the <div> at the end (this div was inside the hook, not in the top.tpl file)
For the CSS declarations you'll need something similar:
5. create a file "styles.post.tpl" inside the same folder "index". From your ftp should look skins/your-skin/customer/addons/my_changes/hooks/index/styles.post.tpl
6. write this code in that .tpl file
<link href="{$config.skin_path}/addons/my_changes/MyStyles.css" rel="stylesheet" type="text/css" />
7. create a file "MyStyles.css" on "skins/your-skin/customer/addons/my_changes folder
so form your ftp should look like "skins/your-skin/customers/addons/my_changes/MyStyles.css
Put all your new css declarations in this new .css file.