BP does not set font correctly to a percentage it sets the body font to 12px – far too small for comfort – and then proceeds to set further fixed pixel widths so sadly it’s not very easy to get a smooth font size change over a layout.
You can change the body font declaration in a child theme stylesheet re-set it to 100% to allow your browsers font-size to be the standard baseline size the site displays fonts from however this won’t really help the fact that there are fixed width font sizes throughout the layout styles but in terms of posts and pages these don’t have font sizes set iirc so changing the body font to 100% should give you a font size on these elements equal to your browser default font size – normally 16px – equally if this is for your purposes only all browsers allow for either text re-sizing or zoom re-sizing of a site which perhaps is a method you could be using.
Thanks Hugo. May I ask for some stepped help here please? This is not just for me – I need the body font by default to be 16px. So as I write a new para I do not need to go to the HTML side all the time to set parametres for font size – which is truly inconvenient – and fiddly for the layman. It is only after I’ve done all my typing that I will go and do font changes. (Have to clean up my home page of my website – a mess of fonts as it was done in an outside HTML editor and putting it into wordpress truly made a mess – but I ran out of time.)
1) Guide to the exact location of file(s) to edit
3) Guide to the exact script lines that I must edit
4) The changes.
I will log in to the konsole – find the file and copy. Then open the original and edit with your indicated changes – right?
If all is well the site should load still….. 
If not – delete original and rename the copy back to the original.
This should keep me safe – right?
Again, thanks very, very much for the help.
The best approach is to create a child theme, this is actually extremely simple, however it does require a number of steps.
1. You need to create a new folder under/in /wp-content/themes/
2. In that folder you need to create a blank file called style.css
3. in that file you add :
`
/*
Theme Name: my theme name
Theme URI: http://buddypress.org
Description: a description – non essential.
Version: 1.0
License: GNU General Public License
License URI: license.txt
Author: yourself
Author URI: ?your site
Template: bp-default
Tags: buddypress, two-columns, fixed-width, whatever other keywords are applicable
*/
`
To do this you will need some form of access to your site server either FTP or via your Cpanel/plesk file manager to create folders /files.
Once you have that done then it’s simply a matter of going to ‘themes’ in the dashboard where you’ll be able to select your new theme.
At this stage as you only have a style.css file BP uses all of the default BP theme files including it’s own styles so activating your new theme will cause no apparent change – good! However you now have the ability to use style.css to add CSS properties/ rulesets that will be read after the BP ones and thus overwrite what may already have been set.
Using the WP editor under ‘appearence’ you should be able to select your child themes style.css and simply add the line:
body {font-size: 100%;}
or:
body {font: 100%/1.4 arial, ‘another font’, sans-serif’}
If the above is too awkward to accomplish then you will probably have to settle for editing the bp-default stylesheet directly and changing the ’12px’ on the body rule for ‘100%’ but those changes would be lost in any upgrades and have to be re-done.
