Whereever you're making your blog, they will probably automagically recognise websites, so all you need to so is type in the address eg http:/ /www.jasperfforde.com (without a space bettween the //) and it will turn into a link:
[
www.jasperfforde.com]
If you're putting a link in here, but you don't neccessarily want people to see the whole address then use [ url=http://www.jasperfforde.com ]text[ /url ] (without spaces in the brackets):
text
But... that code probably won't work on your blog - instead you'll need propper html. use <a href="http://www.jasperfforde.com">text</a> to do the same job.
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That statement is either so deep it would take a lifetime to fully comprehend every particle of its meaning, or it is a load of absolute tosh. Which is it, I wonder?
Terry Pratchett, Hogfather