If you want to have fancy rounded buttons in your Ecwid store, add the following code to your custom CSS theme.

Important note: IE will not show rounded buttons, because it doesn't support the "border-radius" property. It will show usual Ecwid buttons. 

button.gwt-Button, #wrapper button.gwt-Button {
  border-radius: 13px;
  -moz-border-radius: 13px;
  -webkit-border-radius: 13px;
  height: 28px;
  background-color: #e4e4e4;
  padding: 0 15px;
}

button.gwt-Button:active, button.gwt-Button:active, 
#wrapper button.gwt-Button:active, 
#wrapper button.gwt-Button:active {
  background-color: #999999;
}

div.ecwid-productBrowser-details-rightPanel div.ecwid-productBrowser-backgroundedPanel {
  min-width:185px;
  width:auto;
}