style 属性更多 specific ，因此它总是会在层叠中最后应用（可怕的！important ！规则不被承受）。

The style attribute is more specific than any selector, so it will always be applied last in the cascade (horrible !important rules not withstanding). Move the CSS to the stylesheet.

a.hover {
    color: red;
    text-decoration: none;
}

a.hover:hover {
    text-decoration: underline;
}

（我也建议这个类的语义名称更多）。

(I also suggest a more semantic name for the class).