Help me please still dont get the transition thing

I’ve searched kirupa a bunch of times for any help, and checked threads and what not and i still dont understand this transition movie thing… not a clue how to do it. masking effect or somehting blah i don’t friggin know… i built this site here…

and i worked some transitions into it but its not set up the ways i think it’s supposed to and when i publish the movie on the best quality its very blockywhen its transitioning …

i mena it’s even blocky now on medium. Basically i would be happy wiht it if it loaded properly wihtout hte blockiness but i stil lwant to do it the right way with these “transition movies”

can any one post links to tutorials, flas, anythin that can help me actually understand this stuff.

thanks !!!