JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="menu">
<li><a href="01/">Ссылка1</a>
<img width="154" height="134" alt="" src="http://javascript.ru/forum/image.php?u=2666&dateline=1244582671" >
</li>
 <li><a href="02/">Ссылка2</a>
<img width="154" height="134" alt="" src="http://javascript.ru/forum/image.php?u=12584&dateline=1328048771">
</li>
</ul>

CSS

#menu img { 
    opacity:0;
    -webkit-transition:opacity 0.6s ease;
    -moz-transition:opacity 0.6s ease;
    -o-transition:opacity 0.6s ease;
    transition:opacity 0.6s ease;
}

#menu li:hover img {
    opacity:1;
}