Kernal Building

[me storage]

Hi i am new to the topic of Building Custom Kernels and i am using ubuntu
12.04.
Recently i build the latest kernel 3.15.0-rc  by following the below
tutorial
http://kernelnewbies.org/KernelBuild
at first it run correctly after that again i build the same kernel at this
time i don't what did i done wrongly it is not working properly .when i am
starting my system it gives the error like "The System is Running in low
graphics mode you have to set manually configure it"  and i tried with grub
previous linux version .it is also gives the same error.
So can any one please help me how to fix the issue or what did i done wrong?
please suggest me any tutorial which will explain what happened internally
when building custom kernels?
Thank you
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