Google had a widely-publicized problem last weekend where they were mistakenly labeling every search result with a warning that the site being linked to could harm your computer. They quickly fixed that problem. But the problem lingers on in GMail. Here we are two days after the original problem. Yet any GMail message that contains a link in it has this warning at the top:

Gmail false warnings

Just be aware that GMail is including this message for any message with a link on it. So don't freak out. Just ignore the message.