Double Clicking/tapping in the right place helps Safari set its zoom to the proper setting when using Smart Zoom.
Safari and the Mac OS support a feature called Smart Zoom. In Safari, a double tap/click will zoom in on the web page. This is a wonderful feature for those of us that our vision isn't what it use to be. Small text can now be made readable.
The zoom value is determined by the cursor location when double clicking/tapping. Make sure to have the cursor over the text you want to fit on screen. The width of the paragraph helps to determine the zoom value. Having the cursor over a blank area on a web page will likely generate unexpected results.
When done with the zoom, or if the cursor placement caused an unwanted zoom, double-click/tap to get back to full zoom.
[crarko adds: In the interest of fair play, you may consider this hint to be a rebuttal of what I said about yesterday's hint. To me, it just shows the wonderful differences in how people make use of their Macs.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20130110134309464