Can a Cover Letter Be Two Pages?
A cover letter CAN be two pages...but may not be optimal.
Why a Lengthy Cover Letter Doesn't Work
A cover letter can be as long as you want but keep in mind that the purpose of your cover letter is to entice the recipient to read your resume and grant you an interview. Professionals are busy and you are going to be very lucky if they even quickly peruse your resume, especially if it is unsolicited. If you become long-winded there is a much greater chance that you will be pushed to the bottom of the pile until the recipient can give it his full attention.
How to Shorten Your Cover Letter
Make your cover letter as succinct as possible while including your intentions, your special skill sets, why you would like to work for the company, and why you are the best person for the position. Give them an enticing taste of who you are, not your complete, in-depth history.
How to Tighten Your Cover Letter Format
A nice tight format would include an introduction paragraph stating intentions, no more than three paragraphs highlighting skill set, concluding paragraph outlining why you are best for the job.