SRO and HTML

I have taken an introductory course in HTML coding, and I was thinking about using some elements of it for some of my posts. For example, I had some images that I wanted to resize with percentages and I also wanted to give them some horizontal spacing (hspace). I also wanted to do some work with tables (the jigsaw method). When I tried it out, the image appeared in the post preview, but when I actually sent it, the post just displayed the coding. I remembered to uncheck "Disable HTML in this post". Later, I viewed my post from a different computer, and the picture was there just fine. I am wondering if this is some fault of my browser, like my AdBlock plugin, and who can or cannot see the image. I'll show you an example:
<center><img src="https://2img.net/h/i130.photobucket.com/albums/p267/digitaldoom/website%20pics/newrunners.png" alt="Sample Image" width="40%" height="40%" /></center>
It makes me wish I knew more about BBCode and how to do stuff like CSS with it.

I'd also like to know what elements of BBCode SRO implements and disallows.
For example, [glow=orange,2]glow[/glow] would be cool for those IE users out there, and [tt]teletype[/tt] would save us the trouble of using

Code:

the code tag.