Your build itself is very nice, but your BBCoding skills are a little limited. For instance, while you make good use of color, a very simple code inserts an image with the information of the champion, skill, or item you entered. For instance:

[ [Name of Champion, Skill, Item] ] *Use without spaces between brackets, gets you Hecarim

[ icon=Name of Champion, Skill, Item_Size=50 ] *Use without spaces separating brackets, get you

These are just some basic techniques for improving your guide. For more information, check out the guide you can find here.

In addition, I'd expand that last section you got there. Be more specific as to your positioning in a teamfight, who you should be targeting first, etc. Not all players know this information, and we want to be newcomer friendly here.

Lastly, have you considered the use of the Trinity Force item on Hecarim in place of Phantom Dancer? It builds from the Zeal, so it gives similar stats to Phantom Dancer. However, I find that the spammability of some of Hecarim's skills makes the Sheen proc very useful. Also, it the slow from the Phage is appreciated, despite your speed. Even if you don't like it, it might be a good thing to add to an "Optional item" section.

Hope this helps your guide improve even more, and you get my +1.