How to adjust font sizes in Drupal 7.x

There is a wealth of scientific literature on readability for people who have "limited" or "partial" vision--about 20% of the American Adult Population.

I will summarize the important points for computer / screen visibility,

Size is the most important factor. 8 pt is TERRIBLE. 12 point is MINIMAL. 14-16 pt is usual,

If user is in Windows 7, the font size can be increased to 125% or 150%. If user does this, the 11 point font is reasonably readable.

Both Explorer and Foxfire late versions have ability to enlarge fonts. Limited vision users are forced to use this method with most websites. It still caused problems when some fonts are not changeable by browser or when there is type in graphics.

Next to size, inter-letter spacing is the next critical variable.

Then comes line spacing. 1.20 to 1.80 times font size seems to be the desirable range,

Serif or Sans-Serif does not seem to make a difference.

Very thin strokes like Avant Guard are harder to read.

Color however is VERY important--not the color per se, but the degree of contrast between foreground and background is critical. Color blindness affects reading rarely. However many drupal themes which have instructions in a grey on a white background are not so good. A yellow on grey might seem distinctive but if they have the same degree of contrast, they are hard to read. Black on white is obviously best contrast, but any dark color on white works. Reverse type is OK provided you do not have a thin font. If font is bold in any light color, that usually works well with any dark background. Always go for contrast.

THere is a Special Font that has been designed by the American Printing House for the Blind. It is called A-Phont. It already optimizes a number of variables like the inter-letter spacing See

http://www.aph.org/products/aphont.html

It is FREE if you are using it to increase readability. For the basic fonts of a theme, A-Phont and nothing else improves the readability a great deal.

People with normal vision have often reported that it is EASIER to read low vision prepared material without ever knowing what that was.

I haven't modified a theme in D7 yet, but if it's like D6 there is a right way and a fast way.

The Right-ish Way: Copy down the Bartik theme from your /themes directory. Rename the theme (to something one-worded and easy to find/replace), then replace the word Bartik in all files with your new theme name. Once you've done that, upload the newly-named theme to your /sites/all/themes directory. Your theme is now its own separate entity, no longer updated along the Bartik maintenance path. This means that your edits won't get wiped out when you update Drupal — but you'll want to watch the Bartik commits for security issues that might need manual patching. Just go to the theme administration page and switch to your new theme.

The fast way: change one line in the core Bartik CSS. This is wrong because you should not hack core. Updates to Drupal will wipe out your changes if you're not careful. And you never know how many single-line mods you'll want to make.

Either way that you decide to go, you'll want to open bartik/css/style.css
After line 12, paste in:

body{font-size:1.2em;}

Where 1.2 can be replaced with any numerical value to increase the size of the text throughout the site. I gotta tell you, though, the body text on your site actually renders at a default 14px, which is perfectly acceptable. Additionally, screen readers don't care about font size. Browsers do, but most browsers include zoom functionality, so your differently-abled users have their own choice to magnify the page or the text.

Hope this helps.

I'm not familiar with the specific theme, but here's a general gotcha.

Any CSS using absolute positioning risks that some content will get cut off or overprint other content when the site is viewed with a larger font size, as opposed to whole-page zooming.

Additionally, it can make overlapping links difficult or impossible to click. It can also make links within content revealed by rollovers impossible to click because the rollover goes away on the cursor's way there.

Finally, there is the issue of the ratio between the smallest font size used and the largest. If I zoom in order to enlarge fonts that are too small, fonts that are too large can become awkwardly large and overrun their containers. That's why, instead of zooming, I have set Firefox to use a minimum font size of 18 points. This setting can also be made in Safari.

IE has a setting Accessibility > Ignore font sizes set by websites which, I believe, uses semantic markup to set font sizes.

Webmasters cannot simply point their visitors to instructions on how to increase the font size on their browser. They must test that following those instructions results in their website still being usable. And they must test that all the ways of enlarging fonts work, since nobody is going to want to follow special instructions just for their website (and won't read the instructions if they already know how to make fonts bigger).