background-position-x and background-position-y aren't cross-browser compatible

Wrong: 
.myStyle{
background-image: url(images/someImage.png);
background-repeat:no-repeat;
background-position-x: 20px;
background-position-y: 30px;
}


Right:
.myStyle{
background-image: url(images/properties_underline.png);
background-repeat:no-repeat;
background-position:20px 30px;
}