Error I can't seem to find the answer to.

• 
  Exception in thread "Minecraft main thread" java.lang.VerifyError: (class: l, me
• 
  thod: b signature: (Ljava/lang/String;DDDDDD)Lrt;) Incompatible argument to func
• 
  tion
• 
  at net.minecraft.client.Minecraft.a(SourceFile:323)
• 
  at net.minecraft.client.Minecraft.run(SourceFile:650)
• 
  at java.lang.Thread.run(Unknown Source)
  

This error occurs after installing flan's mod loader. Am I missing a step that is not in your wiki?

That didn't work. Now instead of showing the error in minecraft, it black screens right after mojang logo. I ran a tester and it came up with

===Simple Minecraft Error Test===

Starting Minecraft...

Exception in thread "main" java.lang.NoClassDefFoundError: net/minecraft/client/
Minecraft
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.Minecraft
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: net.minecraft.client.Minecraft. Program will exi
t.

Finished session

This is the error I got from running mcverror, I was using 7zip, and this time I tried winrar. Should I clear out mine craft and reinstall it. Just backup my saved maps?

Checking for Minecraft launcher (minecrafterr.jar) in C:\Users\Tyler\AppData\Roaming\.minecraft\minecrafterr.jar
Minecraft launcher found!
Starting launcher...
27 achievements
182 recipes
Exception in thread "Minecraft main thread" java.lang.VerifyError: (class: qz, method: a signature: (Ladg;DDDFF)V) Incompatible argument to function
at ahu.<init>(ahu.java:41)
at ahu.<clinit>(ahu.java:9)
at net.minecraft.client.Minecraft.a(Minecraft.java:395)
at net.minecraft.client.Minecraft.run(Minecraft.java:732)
at java.lang.Thread.run(Unknown Source)
Error report complete.

Well that one was easy.

You installed mods with a minecraft version different than the one you're using.