When astronomers discover a new planet at the right distance from its star to have temperatures that can support liquid water and mainstream news sources report: "Astronomers discover habitable planet!"
First of all, distance from the star is not a guarantee of survivable temperatures; Venus is within the Sun's so-called "habitable zone" but its atmosphere full of greenhouse gases (96% carbon dioxide) make it the hottest planet in the solar system.
Even leaving that aside, just because a planet isn't hot or cold enough to quickly melt/freeze any human who lands on it doesn't mean it fits any meaningful definition of "habitable." The presence of water is hardly guaranteed, atmospheric oxygen is unlikely, and an atmosphere can be poisonous even if adequate oxygen is present.
And then of course, there's the issue of size. In a choice of language so appalling it really should have been in the opening sentence (or its own entry), many reporters have chosen the term "super-Earth" for a planet which is in its star's habitable zone but much larger than Earth. For example, the (relatively) recently discovered planets in the Gliese 667 system are maybe 10 times the size of Earth, so even leaving aside the issues of surface temperature, water, and oxygen, they're "habitable" only by a definition that forgets how gravitational forces are proportional to mass.
The discovery of a new planet is always interesting but badly-written headlines just bug me.
Addendum: This post was sitting unpublished in my drafts for some time, so it's gone a bit stale; the discovery of planets orbiting Gliese 667C was some time ago. Still, the principle remains unchanged so what the hell, up this one goes. If stale posts bug you, put that on your own blog.