There are a lot of people who use glasses and I am one of them, I went to a well known site that had the ability to let the browser make the text as large as possibel by the use of the [+ & -] key and that was one of the reasons I liked that web site .
I thourght they all did?....do you have any examples of sites that dont?
BTW your post is in the wrong topic this is for suggestions for this site (Frihost)
...but it is very polite. Your audience will like it.
So try to specify text size proportionally, eg. 150% instead of 18px.
Just do this, Ctrl+Scroll on mouse, that should make it bigger or smaller. That simple.
If the site has followed proper accessiblity guidelines then this is a functionthat your browser will allow you to do. The style of enlarging text through the site itself is less common as to the extra programming envolved with this functionality. I do believe that sites should follow standard accessibility guidelines. Beyond tat you are showing the users of your site that you are accomidating their needs and this is always a good thing for making your site sticky.
Depending on whether or not the site uses CSS to style it's contents, you may or may not be able to resize the text. If the font sizes are defined in exact pixel values (eg. 5 px) you will not be able to resize the text unless you replace the site's stylesheet- but, if the font sizes are defined in percentages (100%) you will be able to resize the text using your browser.
So - get learned, son!