I want to maximize page wituot loose the proportion! Thanks.

This is all based on how the webpage was programmed.

I'm assuming you want to be able to maximize the window, without the contents of the page stretching to fit the page.

Only some websites are designed with a fixed width. Most however, are designed to accommodate any width. I am unaware of any extensions or addons for browsers which fix the content of the page. I'm sure there might be a script for GreaseMonkey, or one could be created. This would require using either Firefox or Google Chrome (or a version of one or the other).

Assume you are unsing IE

Right click on i.e. icon and choose peroperties
-use dropdown box there and change to Maximized and click Apply

Open IE, max screen
-Hold down the shift and ctrl keys and then click on File in the menu and choose Exit

This works 60% of time

If you are the one programming the page, or have influence over that person, you could suggest using css to create the page with a fixed width, or just certain content.