I was looking at my Blog template and I realised that Blogger sets the text size by pixels, so if you have your browser set on large text it will look exactly the same size as it does on a browser with small text size set.
I didn't like that idea because there are a lot of people surfing the web with poor eyesight and it bothered me that sombody like that wouldn't be able to read my page. So I have replaces all the text sizes with percentages. And now the text on all my pages (including comments) resizes itself to the size set by your browser.
Give it a try
View > Text Size
Anyway below is a conversion table to help anybody else who wants to convert the px values to a percentage on their templates as I have.
43 Title === 270%
18 date header === 115%
16 post title / blog comments title === 105%
15 post / blog comments === 95%
12 Top right description / side bar ==== 75%
10 post footer / margin bottom === 65%
Example:
Old
font-size:15px;
New
font-size:95%;