used in cards indicates the hearts suit. It is shown in the color red. In HTML, the proper way* to show this is ♥ .

see also:      

* Is it my fault if NS 4 is too stupid to display things properly? No. If you really, really, want to do it correctly, you could decide it on the server side, and dish out &hearts; or <img src=... (although one problem with the image is that it will be a fixed size), depending on the user-agent (browser). I'll stick with the correct way, though, and not worry about breaking browsers that are not implemented correctly (which is probably all of them, but that is a whole other rant).