Smashing Magazine’s study of blog design provides a good insight of the design trends/patterns are mostly used by top blogs on the internet.

Excerpt from the article

large blogs require a multi-column layout solution (usually 3 columns suffice) (58%);
layouts are usually centered (94%),
layouts usually have a fixed weight (px-based) (92%),
the width of the fixed layout varies between 951 and 1000px (56%),
58% of the overall site layout is used to display the main content,
CSS-layouts are used (90%),
the background is light, the body text is dark (98%),
the most usual (not necessarily most user-friendly) line length lies between 80 and 100 characters,
Verdana, Lucida Grande, Arial and Georgia are used for body text (90%),
the font size of body text varies between 12 and 14px (78%),
Arial and Georgia are used for headlines (52%),
headlines have the font size between 17 and 25px.

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