Don't write a resume.
Instead of sending out a resume, talk about who you are. Whenever someone asks for something in writing to send to a contact ask to speak to the contact instead. Don't post a resume online but do post to blogs and other websites in your field.
WHY NOT - we often rely on resumes - sending them out blindly - be deleted or discarded. When we talk to people directly we have a better shot at making the right contacts and selling ourselves.
You got the job offer and then they withdraw it. No explanation, no reason, no nothing. So what happened? It could be economics but it could also be some information that the organization gets on you that puts you in a bad light. For example the degree you said you had in your application is not actually complete - although it probably will be next year - but the employer doesn't like that. You told a fib and you got found out. Or the company finds out that you were a pain in your old job and your boss didn't like you. The company contacted your old employer and found out you were not Mr or Ms Popular. Or you send a thank you note which has a bunch of typos in it and the company decide you blew it.
So what can you do?
You can ask. You can ask to find out more information on why the offer was reduced. If you persevere then you may get an answer. If you know then you can either explain or learn for the future.
If you know there is a problem - e.g. your boss will say bad stuff - then warn your new employer and explain why - and give some references who will say positive stuff.
So you got the offer and you're packing your lunch for your first day and you get a call. And the company says thanks but no thanks. Can they do that? Sure. Unless you had a signed contract - which most people don't - and which probably has some clause on page 23 that says that they can.
And why would Mr. Employer do that? Money. Bad results or even worse? New directive from a big cheese? Change of executives means you are not the flavor of the month anymore. All kinds of things.
What can you do?
Keep in touch. Keep communicating. Meet up with the boss before your official start date. Visit the company ahead of time if possible. Keep researching the company. And if something doesn't make sense or looks strange then ask questions - lots of questions. You may not be able to do anything but you can be prepared. If things look dicey or risky at a company then you can start looking for a plan B, hold back on any big plans like moving or buying a new car on the strength of the job or just be emotionally ready.