A beginner's guide to marth should (in my opinion) focus on one big point: get your opponent above you.
There actually aren't that many totally bad things about this guide, but please de-emphasize Dancing Blade, it has a lot of vulnerability.
You should mention the following:
TIPPERS! At one point you say tipper is a bad thing. No! Tipper is one of the reasons Marth is so good. You should talk about how even though Marth doesn't have a projectile, every one of his moves is like a mini projectile in that he can hit his opponent from outside of their range, and on top of that, it's his sweetspot.
Dtilt can shield poke and is good for threatening your opponent's coming at you.
Upthrow is really good coz it puts opponent above you.
Downthrow is really good coz it knocks your opponent around.
You might want to mention that the sweetspot of Dolphin slash is right at the start of the attack, so it should be used right on top of your opponent.
Dsmash has a lot of lag.
The premise of your matchup section is kinda unfounded. It is true that Marth's worst matchups are top-tiers, but that's redundant b/c of course the top tiers are everybody's worse matchups. You should instead provide tips for dealing with each matchup, rather than repeating info you already mentioned earlier in the guide.
Your combo section could use a little work. Ftilt typically doesn't combo b/c the sourspot isn't strong enuff and the sweetspot sends them too far away. You might be able to get a dash attack in, but that would be more of a lucky hit than a combo. You should include:
1. Fair -> Fair, Tilts, Grab, etc
2. Uair -> Fair, Tilts, Grab, etc
3. Dtilt -> Fair, Tilts, Grab, etc
I dunno, I never really describe specific followups, so I dunno what beginners want. I personally would advise beginners to have 2 types of combos: damaging ones and finishing ones. But do note that melee doesn't really have very many combos (compared to the N64 version). But maybe beginners are more concerned with what they can pull off against other beginners. Your choice, just make sure to revise/expand it.
Also, when ppl give you criticism, please stop acting as if ppl expect you to be mango or m2k. That response is redundant.