Even font-size can make a big difference
Well designing your own website/blog has never been easy. You have to think both in terms of the visitors as well as Search Engine Bots; Often it turns out to be a tough trade-off. You pay enough attention in choosing the most attractive layouts, adding some decent colors, or using a JPEG/GIF/PNG art-work to give your site a distinctive look. Me, although not a great fond of flash, still some websites continue to use it. Also I think there is no harm in adding a flash-intro if it is reasonably brief and with a skip-intro option.
But while designing website, how often do we consider adding the best-fit font-size? But to optimise your conversion rate, and to get visitors sticking to your web pages - font size is extremely important. Specification of font size is done in pixel, point or a more generic em unit; and it is extremely difficult to set any standards for font size as it depends a lot on the type of visitors you are targeting as well as theme, layout and overall design of a website.
Based on your own standards of smallest font size, you can set your font size to at most three to four different levels: Tiny, Medium, Large and Largest; Now you need to use them carefully to help visitors reading your content without much difficulty.
Now here I want to mention a minimum font-size guideline:
Microsoft: 11px Tahoma
Apple: 11px Lucida Grande Regular
Also, setting your body font-size to 70% will help you to set the font size of your web pages in terms of em.
But this is just the minimum font size using which you can write your text. Depending upon your website layout or design - it may sometimes look dull and some other time professional. It all depends entirely on the content type.
I just make a quick check at eBay and Amazon, and it was not surprising that both of these websites use rather a medium font size targeting a more general class of audience. You can also check sites like rackspace.com to get an idea of how tiny fonts help sites looking professional. And do not forget effective use of big fonts in some single page promotional web sites - that too works fine for the TG, believe me or not.
And before conclusion, i must say that it is always better to set font size in terms of ems and not in terms of px, or pt, and always use CSS to set font-size.
And one final note: setting the right font-size will definitely improve your site traffic as well as ensure better cross-browser compatibility.
A must read guideline by Adobe