Styles error

Hi.
I tried adding my own style and keep getting the following error when trying to save.
“error : – Invalid characters, please enter another!”

The code I am trying to add is:
{
border: 5px solid #111E6C;
border-radius: 5px;
padding: 5px;
text-align: center;
font-weight: bold;
margin: 0 auto;
display: inline-block;
}

I am not sure what the problem is.