There are lots of ways to credit a blog or online posting. Attribution ranges from an informal mention to a formal citation.

Some of the means of attribution:
Hypertext link to the page;
A mention of the URL (non-clickable);
A mention of the blog's title, author, date and/or entry heading;
A formal citation that includes blog title, author, date, entry heading, and URL;
A screen shot of the blog page and/or its source code.