If you need to adjust the font size on websites then look at:

• Default FullZoom Level - https://addons.mozilla.org/firefox/addon/6965
• NoSquint - https://addons.mozilla.org/firefox/addon/2592

If you need to increase the font size in the user interface as well then you can increase the String pref layout.css.devPixelsPerPx from 1.0 to 2.0 in 0.1 steps to see what works best.
In Firefox 3.6 and later this pref is a String value parsed to a float and allows to fine tune the dimensions of all elements more precisely.

To open the about:config page, type about:config in the location (address) bar and press the "Enter" key, just like you type the url of a website to open a website.
If you see a warning then you can confirm that you want to access that page.

See also http://kb.mozillazine.org/about%3Aconfig

My problem is that i want to enlarge the entire page not just the text... can anyone tell me how to do that?

Did you check out the suggestions in my above post and looked at the extensions?

Firefox supports full page zoom: View > Zoom

See also:

• http://kb.mozillazine.org/Zoom_text_of_web_pages
• Font size and zoom - increase the size of web pages
• Font size and zoom - increase the size of web pages