uses IWHTMLTag; 写在之前

procedure TIWForm1.IWButton1HTMLTag(ASender: TObject; ATag: TIWHTMLTag);
begin
  ATag.AddStringParam('style', 'FONT-SIZE: 30px;  width: 100px; background-color: red;  border-radius: 15px; border: none; color: white; text-align: center;line-height: 50px; cursor: pointer; FONT-FAMILY: 楷体;');
end;

width: 100px为宽度

height: 50px;为高度
background-color: red;背景色
color: white; 字体 颜色