put these marks in the text, then write the item/character/mastery whatsoever, or just simply check out guide to creating builds...
About the build itself, it seems pretty much ok except that i don't like starter items. If you don't really suicide you don't need that many potions early game, you should get some better starter items.
I like Shurelya's Reverie on Janna, but Rabadon's Deathcap is just too expensive and I have this hunch that if you build that much AP on Janna your team will nag about it the whole game, because they expect you to build more aura-support items. But I think Janna is good with AP items, her shield scales well.
I also think you don't need tank items like FoN or guardian angel, because you can escape fast and you should never go in first.
I also think you should take shield spell earlier, but otherwise seems pretty much ok.

Thx, This is the first build i make so...Anyways how do i add those pictures of like items and such in middle of the text? :P

Extensive guide on how to play a good support Janna i read through and you carefully explain how to be the best support you can. i think you should add a couple of things like a section explaining a change in items depending on the enemy team. For example if the enemy teams carry is trydmere shouldnt you get a frozen heart instead of FoN ? << just a suggestion.. .... .. . . . All in ALL a good buil/Guide on how to play a support Janna (+1)