you must use the following properties for a button element to make it transparent.

Transparent Button With No Text

button {

    background: transparent;
    border: none !important;
    font-size:0;
}

Transparent Button With Visible Text

button {

    background: transparent;
    border: none !important;
}​

and use absolute position to position the element.

For Example

you have the button element under a div. Use position : relative on div and position: absolute on the button to position it within the div.

here is a working JSFiddle

here is an updated JSFiddle that displays only text from the button.