Right now, if you have the Minima template installed on your blog, the maximum width of your blog is probably set to 660 px (pixels) wide. If you were to break this down: 410 px have been given to the main body text of your blog, 220 px are set aside for your sidebar and the remaining 30 px serves as the "gutter" separating the text of your blog entries from the sidebar. Playing around with these numbers will change the look of your blog.
One thing to note, however--there are still some people who have 800 x 600 resolution monitors. If you decide to change the dimensions of your blog to 1000 px (because this looks great on your monitor, which is 1280 x 800) then the content of your blog is going to run off the right side of their screen. That's not very professional looking...
Probably the widest you should go is 780 px. Just divvy this number up between your main body text and your sidebar: 530 px for the text, 220 px for the sidebar and 30 px for the gutter.
Where do you enter these magical numbers? Click on Edit HTML on the Page Elements page and follow these directions:
1) Scroll down to where you see the title Outer-Wrapper. You'll see that here is where the numbers are entered in!
2) Change 660 px to 780 px. Change the "main wrapper" from 410 px to 530 px. The sidebar wrapper and "padding" you can leave as is (220 px and 10 px).
Now, one more thing has to be done so that your pretty banner will be perfectly centered over your text:
3) Scroll up a little to the section entitled Header. Change the width from 660 px to 780 px. Now Blogger knows the right number with which to center your banner and everything will be lined up perfectly!
