well i dont care about the others , cuz i love this build

ok so i see a lot of people told u that armor pen runes is not the best idea and i agree with that but only for farming purpsose. i have played armor pen cait and its a million times stronger but when u play pen u cannot also start with boots cos then u have like 54 ad and last will be a prob. so i suggest maybe getting the dorans if u insist on playing armor pen(which i think is stronger anyway) last whisper is a stupid as item and glad its not in ur build. Black cleaver much much more powerful.

On the topic of knowing who your enemies are; if you play either draft pick or ranked play, you will be able to see who your enemies are ahead of time, allowing you to plan ahead what masteries, rune page, summoner's spells, etc you want to take.

I like the guide, noting a few mistakes and as for the runes, I think the first comment explained pretty much on that matter. I would not build straight AS, while I know what your going for here, since I've done this type of build before, I know from experience, that AS is not a main priority, taking some health gives a great advantage in game an 1v1'ing. Bloodthirster will save you a lot of times, and is a very good choice, two Phantom Dancers is not a good choice if you want AS instead of PD get Tri-force, it gives around the same AS, gives HP, and Sheen proc., it's a lot of money, but worth every cent, IMO, it helps you a lot, when fighting. Black Cleaver is not neccesary, while your going for AS, damage is more important for an ADC, so try getting both, Madred's Bloodrazor comes to mind.

The runes, instead of getting MR, I would get either, HP or AD, MR is good an if you feel it is that needed, get scaling ones. Statisticly it gets the smae ammount at level 9, as the flat MR.

Chapters, try putting in more information in the SS chapter (summoner spells), as well as alternative spells. Items are the most important things in a game, so the deserve to get a chance as alternative ones, attempt to throw in a few alternative items.

This guide needs work and I hope you put some into it, PM me when you do and I might change my opinion, no vote for now. :)

Thanks for your suggestions.
1.
Your right, that Black Cleaver is not the best choice against tanks with lots of amor. I use it, because it gives more attack speed, which my build is based on. Maybe I change it, but have to think about it and play it first.
2. The problem is, that I dont know, who will be my enemy untill I'm in the game. But i will think about it too.
3. Just fixed it.
4. That's right, but normally I dont have to recall until I have enough gold for B.F. Sword and Vampiric Scepter. So there's no need for Doran's Blade.
5. Yeah I know, I have to add a lot. That will be done, but not today ;)
6.Good idea! I'll do that and fix all mistakes.

Again thank you very much for your suggestions.

Your build is not representative of the type of build an AD carry will have most games. Let my explain my reasonings behind I can't upvote to you.

1. Greater Mark of Attack Damage and Greater Quintessence of Attack Damage are far better for several reasons that the armor penetration alternative. They provide better auto attack harass, stronger farming, and more damage off your skills that scale with AD. One of the reasons you may need to take these armor penetration runes is because you don't build a Last Whisper late game. Compared to the Black Cleaver, Last Whisper is far more effective at getting by tanks with large amounts of armor. The Black Cleaver is only ever effective if no one on the enemy team has stacked large amounts of armor. In general, the percentage armor penetration is much stronger than flat.

2. Greater Glyph of Magic Resist might be a good choice if you're against a lane with a support that has high early game damage, such as Sona or Alistar, but Greater Glyph of Scaling Magic Resist scales much better into the late game. Additionally, Greater Glyph of Scaling Magic Resist equalizes with Greater Glyph of Magic Resist at level 9, meaning that you'll be set in time for early dragon fights where the enemy AP Carry might be involved.

3. You messed up the link in the masteries section. It leads nowhere, and the link shouldn't show up, but a picture of your masteries in its place instead.

4. Consider 1 or 2 Doran's Blades for lane dominance and a bit of health to help in the early to mid game stages. Since Caitlyn tends to naturally dominate lanes due to her harass and long range, I generally only buy 1 on her, but two is perfectly viable.

5. Your guide is nothing but an explanation of your build, and contains no strategy or tips on how to lane, or teamfight as Caitlyn. Consider adding these sections in your next update.

6. Even though English isn't your native language, consider running the guide through a spell check to fix the mistakes. They are numerous and a couple times it is difficult to understand reading it the first time through.

Good luck, and I hope you continue to expand and improve your guide.