Hi,
The code i stated for pointing to the CSS file can be used in your templates only if your CSS file has a more refined path, like: The file in under a folder called 'Styles' under MIME Objects folder. The correct folder path from under the 'MIME Objects' folder should be written in place of the bold content.
However, if you have just placed your CSS file directly under the MIME Objects folder, you can specify the filename in the parameters tab for that Internet Service ZSCWM/RFUI in se80 only. Then there is no need to add any linking in the HTML template.
~ITSMOBILECSSINCLUDE MOBILE
This should be enough to recognize the CSS file.
Let me know.