The front brake rotors can warp and cause a vibration when braking. The rotors will need to be machined or in cases where they are worn to thin, replaced to correct this issue.
Car Problem Reports
Honda Accord Hybrid Warped Front Brake Rotors May Cause Vibration When Braking
Honda Accord Hybrid Problem
Visitor, 2005 Honda Accord Hybrid, 33,000 mi
At around 33K started getting severe vibration while driving at highway speed. Did not note the problem when braking in the city. When I notified the dealer during the warrenty period they claimed they did not know what was causing problem after the shaving the dics. Now at 87k they say it is definitely bad front disc and i need to replace them