Media Query in CSS Not working as expected

I need to show two different logos on my site depending on the device width. If the screen size of device is 300px or less than it, i need to show small logo.

Site: http://www.geekdashboard.com/

Logo.png -> http://www.geekdashboard.com/wp-content/themes/geekdashboard/images/logo.png

logo-small.png -> http://www.geekdashboard.com/wp-content/themes/geekdashboard/images/logo-small.png

CSS:

.header-image .site-title > a {
    background: url(images/logo.png) no-repeat left;
    float: left;
    min-height: 90px;
    width: 425px;
}

and CSS for small width devices as follows

  @media only screen and (max-width: 320px) {

.header-image .site-title > a {
    background: url(images/logo-small.png) no-repeat left!important;
    width: 300px!important;
}

}

This code is not working as expected for me. I can still see the logo.png even on devices with screen size less than 300px Thanks in advance

Solution

Specifying the media type should work fine.

@media only screen and (max-width: 320px) {
    .header-image .site-title > a {
     background: url(images/logo-small.png) no-repeat left !important;
     width: 300px !important;
     }
}

@media only screen and (min-width: 321px) {
    .header-image .site-title > a {
    background: url(images/logo.png) no-repeat left;
    float: left;
    min-height: 90px;
    width: 425px;
    }
}