I have a div that refuses to change background colors when I hover over it. It stays the same. Here's the code.

HTML:

```
<div id="login"></div>

```

CSS:

```
#login {
    position: fixed;
    float: left;
    background-color: none;
    margin-left: 1.5%;
    top: 1em;
    height: 1.25em;
    width: 7em;
    text-align: center;
    border-radius: .3em;
    opacity: .5;
    padding-top: 1em;
    border: .18em solid gray;
}

#login:hover {
    background-color: gray;
}

```