[html] How to write :hover using inline style?

Not gonna happen with CSS only

Inline javascript

<a href='index.html' 
    onmouseover='this.style.textDecoration="none"' 
    onmouseout='this.style.textDecoration="underline"'>
    Click Me
</a>

In a working draft of the CSS2 spec it was declared that you could use pseudo-classes inline like this:

<a href="http://www.w3.org/Style/CSS"
   style="{color: blue; background: white}  /* a+=0 b+=0 c+=0 */
      :visited {color: green}           /* a+=0 b+=1 c+=0 */
      :hover {background: yellow}       /* a+=0 b+=1 c+=0 */
      :visited:hover {color: purple}    /* a+=0 b+=2 c+=0 */
     ">
</a>

but it was never implemented in the release of the spec as far as I know.

http://www.w3.org/TR/2002/WD-css-style-attr-20020515#pseudo-rules