Can employers see my past work experience/jobs?

They can't "see" the past experience, they have to call your previous employers and talk to them. In today's environment, many companies have rules against giving references beyond the dates of employment, job position, pay rate and if the person is eligible for rehire. A no to the last question implies problems. Also, if there is significant networking between employees at your old employer(s) and the new one, many times there will be "unofficial" communication.

no, they cant. but maybe small business are more "flexible" than larger ones.

If its really bad, leave it off your CV... and be ready and able to explain any gaps in your employment history. Before leaving someone as a contact for a job you had, go meet them in person and ask them for an honest appraisal of your work and any feedback they have. Some of them may have liked you on a personal level but found that you just weren't suited to the role... You may be able to build on this in an interview, turning a bad thing into a positive. With the jobs you left at short notice, be prepared to explain why you did this, employers don't like someone that comes across as unreliable, in some circumstances you aren't required to give notice anyhow. I've been down a similar track in the past, its not always easy and it really does depend on circumstances i guess but all i can really say is just highlight your strengths and address your weaknesses with the attitude that you are aware of them and are working at improving in those areas.. I find it hard to sum up my net worth on paper and find it much easier to meet employers personally and build a good rapport with them before they look at my CV.... again it all depends on the type of jobs you are going for... Use common sense, eye contact and a smile, and remember to be flexible. If you are going for any kind of hospitality job, never ever apply for a job during peak service times! I was responsible for a lot of hiring and firing in my former job, and anyone that brought me a resume or tried to apply or inquire about positions during peak service times of before 10am (breakfast service) between 11.30am and 2.30pm or after 5pm (dinner service) promptly had their applications/resumes thrown in the bin. Some of these people on paper were awesome! but obviously lacked common sense, something that is an instant no deal as an employer. Best of luck to you!