To unblock the American Greetings Ecards site on your Mac, follow these steps:

1. Check Internet Connection
Ensure that your internet connection is active. Open another website to confirm connectivity.

2. Review Browser Settings
Sometimes, browser settings can inadvertently lead to a site being blocked. If you are using Safari:
- Open Safari and go to Preferences from the Safari menu in the top-left corner.
- Select the Privacy tab.
- Ensure that "Block all cookies" is unchecked, as it can affect site access.

3. Disable Browser Extensions
Extensions may interfere with website access:
- Click on Safari > Preferences.
- Select the Extensions tab.
- Disable any suspicious or unnecessary extensions by unchecking them or clicking "Uninstall."

4. Clear Browser Cache
Old cache files can sometimes create issues:
- Go to Safari > Preferences > Privacy.
- Click on Manage Website Data.
- Select Remove All to clear all stored data.

5. Check Firewall Settings
Your Mac’s firewall might block certain sites:
- Go to System Preferences > Security & Privacy.
- Select the Firewall tab and ensure that it's not blocking Safari or other browsers.

6. Modify DNS Settings
Changing your DNS can solve site access issues:
- Open System Preferences and select Network.
- Choose your active network connection (Wi-Fi or Ethernet) and click Advanced.
- Go to the DNS tab, then click the + button to add new DNS servers, such as Google's (8.8.8.8 and 8.8.4.4).
- Click OK and then Apply.

7. Try Accessing the Site in Another Browser
Download another browser like Google Chrome or Firefox, then try to access the American Greetings site there.

8. Check Site Blocking
It’s possible that the site itself is facing issues or that your internet provider is blocking it. Visit online services that check if the site is down globally.

9. Contact Support
If all else fails, reach out to American Greetings customer support for guidance on accessing their site on Mac. You can find FAQs or help topics at American Greetings Help Center - [learn more].

Following these steps should help resolve the issue of the site being blocked on your Mac. If you continue to experience difficulties, further investigation into network settings or service blocking by your ISP might be needed.