The reason is that the SHA-1 hashing algorithm is being deprecated by most Certificate Authorities. Please review this article for detailed information.
Starting in November 2014, SHA-1 will be gradually sunset by Google. Thus, we strongly suggest that anyone using SSL certificates signed with SHA-1 reissue their certificates from Namecheap account panel as soon as possible.
If you are not sure whether you SSL certificate is signed by SHA-1 or SHA-2, check our KB Article for a tool to check this."