Magento transactional email shows and old template even after styling it

Make sure the emails you've edited are choosen under System > Configuration > Sales > Sales Emails > [type of email] > [type of email] Email Template / [type of email] for guests

Other emails like the one for welcoming a new user are spread out over the System > Configuration, for example under Customer Configuration > Create New Account Options. You'll have to locate the email templates you have updated.

By default all these dropdowns are on [...] (Default Template From Locale), select your modifications name from the dropdown

Have you assigned these templates in the system configuration for the store you're testing?

After creating a transaction email template you need to tell the store to use this for the relevant email.

So for example the New customer email is assigned in System Configuration -> Customers -> Customer Configuration -> Default Welcome Email