How should I use ( I mean the guidelines ) and how should I cite ( I mean how to write the source) a picture or diagram from any website without violating the copy rights? Thank you.
You need to cite images, diagrams and artistic works as you would cite any other type of work.
The citation format should follow the bibliographic style that you are using for your text, i.e. APA, Harvard, Chicago, MLA systems. A number of referencing systems are used throughout the University and the examples, given here in APA format, are guides only: be sure to look up the correct style used in your area and refer back to your favourite style handbook if in doubt.
more details http://sydney.edu.au/copyright/staff/citing.shtml
Look also in http://rmit.libguides.com/content.php?pid=220068&sid=2391438
In-text:
Figure 1 (Margund Sallowsky 2006) shows the innovative building design at Brunswick Campus.......
Note: Just include the Author and Date for In-text reference.
In -reference list:
Sallowsky, M 2006, RMIT buildings - Brunswick campus, digital image, RMIT University, Melbourne, viewed 12 January 2012, .
As for the copyright issues, I think it would be best if you asked for permission of the copyright owner before making use of the pictures. In most websites there are ways to contact the owner of the website. Usually they are the ones who own the copyright to the pictures on their site too. Just write to them asking for their permission and in most cases they will happily say yes. Some may ask that you acknowledge them in your work. So you say something like "Picture printed with permission of ...[name of copyright owner] ...."
Coming in to this late, but I wanted to make a note here in case anyone comes across this question in the future. Citation/attribution is actually not relevant to whether use of a picture/diagram in the paper itself is copyright infringement. Using it MAY fall under fair use (or other applicable copyright exception), but attributing it properly does not impact that. Though of course, attributing a source properly is good ethical practice either way, and would ensure that it was not mistaken for plagiarism.