Rather than doing website header verification, we strongly prefer using our pre-built verifications in the Website SEO page or DNS verification if possible.
Pre-Built Verification - Best Way
For Pinterest and Facebook you can verify links in Admin > Settings > Website Settings > SEO Settings - Facebook and Pinterest Verifications. Note you should use just the code rather than the entire string with html.
Route 53 Verification - Second Best
This would involve adding a TXT value or similar to the Route 53 DNS entry that we manage on behalf of all Floranext website customers.
Add Header - Third Best
Our system does allow you to add code directly to the html head, but this is not the best option. If necessary you can update in System > Config > Designs > HTML Head > Miscellaneous Scripts > Paste code here with no quotes.