U wanna fill 20 pages but dont have that much info... right?
Firstly google for ur guidelines and collect the webpages, even they might seem useless or dont contain the info u need.
Then try the following: (
I try it in exams, and mostly, I TOP 
).
Give a seperate page for each guideline, e.g. on 1st page, profile of the site.
In it, type whatever u got by googling 4 guidelines. Use words like
"According to the principles of e-com..."
or
"As told by e-com guru Tom Coax..."
or
"As far as profile is concerned, the followings need to be included in it...."
Use words like,
"When we look at project from a developer's view, we see..."
or
"Generally, end users are concered with only..."
or
"The main purpose of the project is..."
or
"The following are the three major issues while discussing the project..."
(U can enter anything by numbering 1,2,3 there....)
or
"When internet was in its early days..."
or
"In the early days of e-com..."
In 'Security issues', u can type everything ranging from encryption, cryptographi to typography. Use words such as RSA, SSL, ISA, MD5, UNIX, Cipher, 128 Bit very often.
For payment terms, go to any e-com site, rip out their conditions page.
For the 'Services offered' page, go to indiatimes.com and take a look at their shopping page.
For 'Selling or Buying options', go to bazee.com
For 'Comments on success or failure...' type some error messages that u can see if u give wrong password in e-com sites, or 404 Page not found etc.
I think U can easily fill 14-15 pages using this much info. Also, it is good to include some source codes in bitween paragraphs by using words such as,
"The following code will make the concept clear..."
or
"For more information about the XXX, the source code can be reffered..."
Then type the code in it in courier font, and draw a box around it.
After including the source codes, the report will be surely 20 page long.
Keep the paragraphs small. choose font as Trebuchet MS.
Give page numbers in white color and black background as it appears on digit special issues.
Don't think I m joking... I really use all these techniques in B.T.E. exams and mostly, I am topper in our class. Whatever I told to include can be also used in orals. When u start 2 talk about latest technology and use the above sentences, examiners don't bother 2 ask u much qstns and give u very good marks, coz they r afraid that we will come 2 know they r fool if they ask us much....
If u need format of project report, I suggest go to pscode.com, search of a program called anveshak, then download its documentaton. It was the bes format of a project report.
B.T.W. Best luck 4 ur project. I would like to hear the results of ur project.