In Firefox this is one of the defaults style, having a dotted lines around the links to be able to remove this you just set the link outline to none in your css.
You can specify what state of the link will border not occur.

a, a:visited, a:focus, a:active, a:focus{
outline: none
}

This is a tip for the newbie on wordpress theming. If you install free themes and your having a hard time controlling your image alignment to left, right or center. This is because your using an older theme, you may not have these styles in your style sheet.
Here are the styles – you can [...]