MOSFET H-brigde resistors.

Hey i just wanted to know whats the purpose of the 10k resistors in this schematic, is it correct assume it is pull-up resistors to stop the circuit from "floating"

The transistors in the opto-isolators can only pull the voltage down. They won't drive the voltage up. The 10k pull-up resistors makes the voltage high when the transistors are off.

My strong advice is to forget that circuit, its got a bad case of shoot-through and will only cause
you trouble.

Note that both high-side and low-side devices are momentarily on together as the gate voltages
change at a transition. This allows very large current pulses to flow in the main circuit. This is
awful circuit design.

Any high power H-bridge has to be designed so that the low side switch is fully off before the
high side device turns on and vice-versa. This means there must be dead-time between switching
one off and the other on. Standard MOSFET gate driver chips do this for you.

Opto-isolation for a 12V bridge seems like overkill to my mind.