The <marquee> is block element or inline element?

I write a html/css code, and find the <marquee> and <span>'s layout is strange:

if <marquee> is a inline element, the span will on the right of the marquee, but if I use the span float right, it will like this:

So the <marquee> is not a block element.

How does the <marquee> display in html?

Solution

You should avoid to use this tag: It's not a standard element. See yourself: https://www.w3.org/wiki/HTML/Elements/marquee

To replace it, you should use some javascript, or use a plugin :

You can achieve to do that in pure css to with animations : http://codepen.io/thomasbormans/pen/EjMBqO

@keyframes marquee {
    0%   { transform: translate(0, 0); }
    100% { transform: translate(-100%, 0); }
}