In the Appearance section, you can select the default theme that external users and you see when arriving at your Weblog. You will notice that the default templates show a “theme bar” at the bottom of the page that looks (depending, of course, on the selected theme) like this:

When users click on one of the themes, the Weblog engine will send them a persistent cookie which pre-selects the desired theme for whenever they come back to your site. The selection you make here applies to everyone who is new to your site or does not have set a preference. If the user clicks “Reset”, the theme will fall back to the default you specify here. The list contains all themes that are registered locally in the web.config (V1.0 – V1.7) your weblog’s main directory. V1.8 does not use the web.config for theme information, see Release 1.8.  Details about registering and designing templates can be found in the Templates and Macros section.

The category filter for the main page is a setting that causes only entries of the given category to be presented on the home page. This is convenient if you do not want your main page to contain and aggregated view of all entries from all categories, which is the default behavior, if you leave this setting blank. There’s one catch with this right now: If you set this value and you have entries that are not in any category, they will not be visible anywhere and, worse, you will not be able to edit them, because they get filtered out in the internal view as well.

The setting maximum days on main page defines the maximum number of days to appear on your home page. This setting only applies to the default page and not to the category pages. This is not a “number of calendar days” value, but a cumulative value. If you have posted only on 15 days in the last year and this value is set to 10, the main page will contain the most recent 10 days of those 15.