不,我不这么认为。Opera 的行为与 Firefox 相同。我想出的最佳解决方案是仅在需要用户注意时才对元素进行样式设置(元素具有焦点或包含无效数据)。
这是我作为 Sass 引导程序的一部分使用的:
@mixin background($image, $bgcolor) { background: $bgcolor url(#{$imagedir}#{$image}) no-repeat scroll right center }
input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]), textarea, select {
    font: inherit;
    // background-color background-image background-repeat background-attachment background-position
    &:required:valid, &:required:in-range {
        //border: 1px solid #0f0;
        &:focus { outline: 1px solid #0f0; @include background("tick.png", transparent); }
    }
    &:invalid, &:out-of-range {
        @include background("asterisk_orange.png", $required-bg);
        border: 1px solid $required-color;
        &:focus {
            background-image: url("#{$imagedir}exclamation.png"); outline: 1px solid $required-color;
        }
    }
}
这是生成的 CSS 的样子:
input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]), textarea, select {
  font: inherit;
}
input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]):required:valid:focus, input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]):required:in-range:focus, textarea:required:valid:focus, textarea:required:in-range:focus, select:required:valid:focus, select:required:in-range:focus {
  outline: 1px solid #0f0;
  background: transparent url(icons/silk/tick.png) no-repeat scroll right center;
}
input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]):invalid, input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]):out-of-range, textarea:invalid, textarea:out-of-range, select:invalid, select:out-of-range {
  background: #fef8b4 url(icons/silk/asterisk_orange.png) no-repeat scroll right center;
  border: 1px solid red;
}
input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]):invalid:focus, input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]):out-of-range:focus, textarea:invalid:focus, textarea:out-of-range:focus, select:invalid:focus, select:out-of-range:focus {
  background-image: url("icons/silk/exclamation.png");
  outline: 1px solid red;
}
input:not([type^="date"]):not([type="file"]):not([type="radio"]):not([type="checkbox"]):focus + .tip, textarea:focus + .tip, select:focus + .tip {
  display: inline;
  position: absolute;
  border: 1px solid red;
  background: #fef8b4;
  margin: 0;
  padding: 2px .5em;
}
值得注意的是,对于 Opera,outline 不会像边框/背景那样导致元素失去其默认样式。