Advertising and custom sizes?

[setishock]

ACP > Forum and Moderators > Forum Blocks Manager > Add Block > Dropdown Menu > Select >> Custom HTML/PHP > Click >> Continue >
You come to the setup window.
Put a title in.
The description box is notes to yourself, I leave it blank.
Leave the cache time where it is.
Select what type of code you're going to use.
Put in your code or plain text. Use the center tags around your code to center it in the block.
Leave the template to use as is.
Then click that all important SAVE button.
When you save it you will get kicked back to the screen where you selected make a block. Under that is a text link that says > Purge Cache. Click it. Let it do its thing and you're done. Well, not quite...
Go to the stylevars and scroll down to forums. Almost half of that is the forum sidebar which is the block(s) you made. Edit those to suite you and then you're done.
Go admire your handywork.