<!DOCTYPE html> is the same as <!--DOCTYPE html-->
Everything in web browser is the same as flowlayout so for iframes
you need a <br /> between them or they will be right next to each other.
eg
<iframe></frame>
<iframe></frame> will be next to each other.
To have them on top of one another you need to do
<iframe></iframe>
<br />
<iframe></iframe>
However <div></div> does <br /> automatically
so you don't have type <br /> for </div>.
writing <!>
is the same as writing <!-- -->
<!DOCTYPE html> is the same as <!--DOCTYPE html-->
Everything in web browser is the same as flowlayout so for iframes
you need a <br /> between them or they will be right next to each other.
eg
<iframe></frame>
<iframe></frame> will be next to each other.
To have them on top of one another you need to do
<iframe></iframe>
<br />
<iframe></iframe>
However <div></div> does <br /> automatically
so you don't have type <br /> for </div>.