Got it! The example had a width attribute with a value set to 600. I removed the width attribute and now the page occupies the entire width of the window.
It seems it is centered and from the IE dev tool I could see that the min-width is set to 750. So it appears that if the width attribute is used, then the page will be centred and based on the width will expand breadth-wise.
Now the question still remains ... from where can I get the tag information for the page component? What other attributes are present for the page tag?
I am sure it is the effect of late night working!!
The link referring to the attributes of page is present in the developer guide