How change size font

Hi,

You can add this in your style.css file or create your new css file so that you can override your own css without touching default style.css file.
for eg : -
1) create filename.css
2) add that css file in your addari.info file (for eg : - stylesheets[all][] = filename.css)
3) and then clear your cache it's in admin/settings/performance.
4) than try to add css in that file & check on your browser.

All The Best

For a start you might wanna use Firefoy with the Firebug add-on. Use it and examine the parts of your page you need to manipulate. You can make changes within firebug and see the results. Firebug also shows you which files contain the lines you have to manipulate "in real life" so that you can experiment without fear and after that change the settings of the files accordingly.

To do that you should use a decent editor (at least wordpad, no wysiwyg!!) but better yet a editor like textpad which can show syntax information and has a line count.

Some reading about CSS might also be useful.

Well, or you check: http://drupal.org/project/text_resize