I want to open up a link (of another site) on new page in iframe. For example when the link on page A is clicked, it opens a new window(Page b) of same website and make the link of another site to open in iframe..
Do you want to embed another page inside another? Would using a template be better (e.g. top and footer) for a consistent look? iframes should be avoided where possible. They don't size well as they are not aware of the height/width of their contents.
There are loads of ways of doing this - you could use an include file for example.
Say the iframe is in index.php and you want to show profile.php in the iframe: