re: Quick grass question: dead spots after cutting very high grass. Best options?

Looks like "root rot". There's a scientific name for it but I'm too lazy to find it (something rizotta I believe). You can see it a lot in hay pastures prior to cutting. Basically the bottom of the grass doesn't get much sunlight due to height of grass, therefore it stays damp all the time. It's a fungus that grows in damp areas and climbs up the stalks. When you cut the long grass/hay, it is exposed and turns a brown color. The sun will now dry it out and it will go away. After a good rain/watering, the grass will return to normal green color. If you keep the grass mowed consistently, you should not have problems with this in the future.