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Hi Bergrar,
By "weblogs" I assume you mean the length of the news items that appear on the frontpage? If this is the case, when you create a new article you will notice that there are two input boxes (if you create it from the admin interface.) The first input box contains the text that will appear on the article summary (and hence the frontpage) while the second box contains the rest of the text that will be displayed when your user clicks on "read more".
As for making a block visible to a non-registered user: in the admin interface click on groups and edit the "anonymous" group. You will see a number of checkboxes that determine which blocks and modules are / are not visible to an anonymous user. Simply select the blocks and modules you want an un-registered user to have access to and update the preferences.