Marquee tag is obsolete, though it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.
Alternative is a little css and html
<div class="marquee">
<p><img src="path/to/img.jpg" alt="blah blah blah" /></p>
</div>
.marquee {
background:#000;
box-sizing: border-box;
color: #fff;
overflow: hidden;
white-space: nowrap;
width: 100%;
}
.marquee p {
display: inline-block;
padding-left: 100%;
animation: marquee 15s linear infinite;
}
@keyframes marquee {
0% { transform: translate(0, 0); }
100% { transform: translate(-100%, 0); }
}