How to add Custom error message in magento

magento

Solution

Added because this question appears in Google.

For a yellow "warning" message (the one you probably want for this purpose), use

Mage::getSingleton('core/session')->addNotice('Please log in to track your order');

For a green "success" message, use

Mage::getSingleton('core/session')->addSuccess('Tracking successful');

For a red "error" message, use

Mage::getSingleton('core/session')->addError('There was an error tracking your parcel');

Problem

I included a link named `track your order` in footer. If user click this link without logged in, it should show error message like `please login to track your order`. I'm new to magento please guide me to do this.

Original source