Work in Internet explorer not in Firebird

Can someone tell me why this piece of code doesn’t work with mozilla Firebird but well with Internet explorer, is there something i could change ?

<img src="index.jpg" height="570" width="820"onMouseOver="this.style.cursor='hand'";
 onclick="PopUp()"
>

In IE, it shows the hand when i rollover the picture not in Firebird

Thanks,

Ubik