Remove all the indents. That will wreck havoc on mobile rendering.
If want the picture centered, use [center][/center] instead.
Edit: This is what it has: [INDENT][INDENT][INDENT][INDENT][INDENT][INDENT][INDENT][INDENT][INDENT][INDENT][INDENT][INDENT][INDENT][IMG]http://img.techpowerup.org/170831/vanguard-banner.jpg[/IMG][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT][/INDENT]
This is what it should be: [center][IMG]http://img.techpowerup.org/170831/vanguard-banner.jpg[/IMG][/center]
There are also indents wrapping the text...those just need to be removed. You can disable the rich-text editor to see them.
This is what all those indents translate into:
HTML:
<div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><div style="padding-left: 30px"><img class="bbCodeImage LbImage" alt="[IMG]" src="proxy.php?image=http%3A%2F%2Fimg.techpowerup.org%2F170831%2Fvanguard-banner.jpg&hash=19feefd64fbb809f6907c7bba6f62bbb" data-url="http://img.techpowerup.org/170831/vanguard-banner.jpg"></div></div></div></div></div></div></div></div></div></div></div></div></div>
Division elements are extremely rigid, hence why it's ruined on mobile.