"Do you prefer a single page resume or multi-page? If multi, then how many pages of resume you think is good enough to sell you?"
Single page. If I absolutely, positively have more to say, I occasionally attach a one-page Appendix, "Sample of Project Particulars," which includes 5 or 6 quick stories about major projects I completed that are relevant to the company and position I'm submitting to.
"Do you elaborate on your work experience (like, job description, responsibilities, etc.) or you want to keep it short?"
Yes, but I wouldn't say "elaborate". More like "itemize". Forget about things like "experience", "job description", or "responsibilities". Focus on one thing only: results. What I did, who it was for, why they needed it, and what they accomplished with it. "Built an AJAX e-commerce site that enabled a $10 million catalog distributor to double sales in 6 months." This shows that I understand the forest in which I'm planting trees. Short, sweet, and to the point. If it catches their attention, they'll ask you more about it. If it doesn't, then you probably don't want to work for them, anyway.
"Do you have more than one resume, like a master one with all details and one-page resume targeted to a particular position?"
Just a custom one pager specially made for each company. I show them the same level of special attention that I expect in return.
"In what order you present information in the resume: Objective, Experience, Skills, Careers, Summary?"
1. Very short summary (with embedded skills) that pretty much says it all, "AJAX programmer, expert level in e-commerce, 100 projects completed, ready for next long term challenge in Big City, USA."
2. Applicable accomplishments in reverse chronological sequence. (Emphasis on "accomplishments".)
"Do you really think the resume layout matters more than the content itself?"
"Which font do you use for your resume? Arial? Verdana? Webdings?"
"Do you prefer to maintain an online version of your resume?"
No. I'll contact them. I don't want anyone contacting me.