I don't like the font used in the documentation as it is too small. There is an old topic (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1259527175/0 here) from Nov. 2009 that I did not want to re-open.
The problem is in the CSS. I cannot change the web site, but if you have kept the web pages from the install (in the "reference" directory) and use then from the Help in the IDE, you can change your own layout. Edit the Arduino.css file; the /*... */ denote comments, your file does not have them. These are from version 0018.
body {
margin: 0px 20px 20px 20px;
padding: 0px 0px 0px 0px;
background-color: #aaa;
font-family: Verdana, Geneva, Arial, sans-serif;
/* Omitted from local file as text is too small...
* font-size: 10px;
* line-height: 15px;
* xxxbackground: url(bg.gif)
*/
}
and to let the width adjust with browser window size,
#page {
/* Omitted from local file as it limits page width
* width: 700px;
*/
}