well nice one indeed ^^
Runes seem fine,masteries too,quite detailed...
I'm used at playing him a bit more tanky with rod of ages or even Rylai's crystal scepter...anyway very nice for a Burst AP build...keep up the good job!:D

decent guide, however, as Fizz is a mostly AP character, you need more AP in the build. One recomendation would be to drop the Doran's Ring mid game and pick up either a RoA (dont get it too late in the game, as it does have a stack that builds on time...), or a Rylai's. Both are very good, both providing mana (RoA more than Rylai's) and AP (about the same each before RoA stacks). RoA is better for survivability/sustain, providing additional health and a nice stacking mechanism, Rylai's is to enhance your innate slowing capabilities by providing a 15% slow on all abilities (yes, all your abilities are either AoE or DoT, thus giving you a 15% slow). Combine that with the slows on both your "e" and "r", you have plenty of means to slow your target.