Need lots of work,

Not just the masteries, runes and build. There needs a lot more coding and effort in this guide before it can get a +1 from me.

1) Runes and masteries need to be revised. 21/9/0 masteries and flat AD quints with armor pen marks.
2) Use some BB coding to spice up the guide itself, it's much easier than it looks.
3) I wouldn't go with a BF sword first, you need a Doran's early on, then rush the zeal.
4) Yeah this one might be a little nit-picky, but it wouldn't hurt to work on your grammar a little. It's not terrible, but definitely noticeable.

Sorry man, downvoted. With a lot of work this could be a decent guide, the item build doesn't seem too far off.

To be fair, the rating is lower than it deserves to be. The build is somewhere there, though not optimum. I've seen much, much worse. So I'll just countervote them with a +1.

I understand people play kog differently, this is just the way I play Kog as a heavy ADC for Mid/Late game. The runes and talents are used to help early game. I have a high win rate with this build, but I'm sure others are more viable.

Okay looking at your numbers, I feel it is NOT personal preference at all. Getting it the other way round is just wrong. Why? You're swapping some 6 arpen for just 1.7 AD. That's not a big difference in terms of ability to last hit. Overall, getting it the 'wrong' way is not viable over getting it the 'right' way.

The most popular choice of runes on Kog'Maw seems to be flat AD on both marks and quints though, which makes sense because he not only could use help to last hit, he also deals heavily mixed damage, including AD-scaling magic damage.

Uh, no, that's not true. Both are viable.

ArPen gives more damage on champions, flat AD makes for easier last-hitting. ArPen marks gives 15 ArPen, flat AD quints gives 6.8 AD. Flat AD marks gives 8.5 AD, ArPen quints give 9.2 ArPen. Therefore, the first combination deals more damage while offering better last-hitting, and the second one deals less damage but still at least has some, but offers even better last-hitting.

It's not wrong, it's just personal preference.

Almost every Kog'Maw player takes Void Ooze at level 1. It's not only your only CC, it is useful for shoving the lane if it pushes up towards your tower.

Please add some BBcode for readability also, turn on 'require comment to vote'.

It doesn't seem as bad as reflected by the percentage of approval, but you could fix the things mentioned above. Kog'Maw is weak early but a hypercarry late, so grabbing even double Doran's Blades and a vamp scepter would not be out of place.

Lots of things wrong about the guide:

1. It's armor pen reds and flat AD quints. Not the other way round.

2. Skill order is most definitely wrong. Void Ooze at level 4 = throw the lane before level 4.

3. I disagree with item build, while a B. F. Sword first is nice, it should have at least one Doran's Blade first. Also, Kog'Maw needs a very early Zeal.

4. Masteries are wrong. 21/9/0, not 24/6/0.

So, -1 from me.