Will this memory work?

Yes.

http://support.apple.com/specs/macbook/macbook.html

512MB of 667MHz DDR2 SDRAM (PC2-5300) on two SO-DIMMs, supports up to 2GB

Click to expand...

MacBook RAM is takes 200 Pin SO-DIMMs.

Does the seller guarantee it is Mac compatible?

If not, how do we know? This Patriot RAM is the correct nominal specification (DDR2-667 200 pin SODIMM), but there are many other specs that are necessary for Mac compatibility that are not disclosed. It might work, it might not.

Why would you buy PC generic RAM from a company that doesn't guarantee compatibility, and has the ability to charge you both shipping and a 15% restocking fee if it doesn't work and you want a refund? (Check their policies under "non-defective returns")

You can get Mac-compatibility guaranteed RAM for $10 -$20 more from one of the reputable vendors recommended by MacRumors readers here such as OWC (MacSales) or Data Memory Systems. Crucial is also mentioned often, they are a little more expensive.

Thanks
Trevor
CanadaRAM.com

Probably...

...and even more so because two of the reviewers on the product page obviously uses Macs... 😉

I use a couple of generic TwinMOS modules, the cheapest I could find on my favourite online computer parts store (which knows nothing about Macs, whatsoever).

But, just to protect yourself, be sure you're allowed to return them in case they're not the right type...

I completely agree with CanadaRAM. You put yourself at a fair amount of risk for marginal savings. OWC, DMS, and others guarantee the RAM. Macs are notoriously finicky about RAM specs, and it's not worth the risk. It might work fine right off the bat and then cause kernel panics a week or so down the road.

It's not like reputable RAM is twice as much... it's only a little more. But, as Mitthrawnuruodo pointed out, other Mac users seem to have had success with what you linked.

I suppose it depends on how risk-averse you are. 😉