I would like to know why my image rollover tags only work sometimes and here's the code I use:

<a href=main.html onMouseOver= "if (document.images) document.Jphoto11.src= 'Jphoto12.jpg';" onMouseOut= "if (document.images) document.Jphoto11.src= 'Jphoto11.jpg';"><img src="Jphoto11.jpg" name=Jphoto11 border=0 alt= '>photos'></a>

Nevermind.