I do not know how to do it in ebay itself or if it is possible for search.
For the forums here, you have a user Profile in "My Setting" to set the font to a larger size. I found the default forum font to be small so I set it to the "Large" font. I have not seen any other eBay settings to set font size.
But I have found that when using different parts of eBay in My eBay views or Selling Manager views and in searches, the screen font sizes changes, sometimes only slightly, sometimes more visible, and it carries forward to the next ebay page I view sometimes.
I use the CTRL 0 (that is number 0 "Zero", not letter O 'Oh") to reset the screen to my default size every once in a while when I find the screen is looking "off" a bit. For example, I just did this CTRL 0 while browsing your forum topic post and it reszes every so slightly smaller the fonts on the page.
So you may want to just reset the screen with CTRL 0 every once in a while like I do. I never could figure out a pattern to this font change issue.
My main browser is FireFox 23.0.1 (have not upgraded to 24 yet) on WIndows XP SP3 (old windows but working fine). I use CCleaner (free tool for cleaning up Windows settings, cookies, temp files, browser cache) before and after each browsing session to keep my computer clean. This seems to make each browser sessions and eBay login work smoothly. The font size issue seems to be reset to normal after each windows session after I clean with CCleaner.
PS For those who do not know, you can use CTRL + to increase size, CTRL - to decrease size and CTRL 0 to reset to the browser default. Works in most browsers.
