Magento 1.9 Error – Fix 403 Forbidden Error in Console

You should only use 755 for directories and 644 for files (they don't need the executable permission).

Use these commands in the skin directory to apply the permissions recursively:

find . -type f -exec chmod 644 {} ;
find . -type d -exec chmod 755 {} ;

The first line finds all files and chmods them to 644, the second line finds all directories and chmods them to 755.

See also: Files and Folders permission issue after I copied all files

You could use use helper method.

<reference name="head">
    <block type="core/text" name="stylescss">
        <action method="setText">
            <css helper="your_module/someHelperMethod" />
    </action>
</block>

And then, in your module helper file, create method, which return string with base url.