This doesn't sound familiar... does Firefox display the block message on the source/destination site, or on a different site?

You may have an unwanted extension that is filtering the pages you see. Try this:

Disable ALL nonessential or unrecognized extensions on the Add-ons page. Either:

• Ctrl+Shift+a
• orange Firefox button (or Tools menu) > Add-ons

In the left column, click Extensions. Then, if in doubt, disable.

Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Does that get rid of the warnings?

You may also need to scan/remove malware. This support article has some recommended tools: Troubleshoot Firefox issues caused by malware.

http://safeweballiance.com/

I question whether this is a legitimate security organization. It's website provides almost no information, the whois information for its domain is hidden behind a privacy service, and the domain was registered less than 3 months ago:

Domain Name: SAFEWEBALLIANCE.COM
Update Date: 2013-08-27 11:52:59
Creation Date: 2013-08-27 11:52:59

Registrant Name: Registration Private
Registrant Organization: Domains By Proxy, LLC
Registrant Street: DomainsByProxy.com
Registrant Street: 14747 N Northsight Blvd Suite 111, PMB 309
Registrant City: Scottsdale
Registrant State/Province: Arizona
Registrant Postal Code: 85260
Registrant Country: United States
Registrant Phone: (480) 624-2599
Registrant Fax: (480) 624-2598
Registrant Email: SAFEWEBALLIANCE.COM@domainsbyproxy.com

See also:

• http://safeweballiance.com/warning.html?my-uq
• http://www.google.com/transparencyreport/safebrowsing/

• http://www.ip-adress.com/whois/safeweballiance.com
• http://www.statscrop.com/www/safeweballiance.com