These are pretty easy to follow rules.

About the page width, remember: If the users need to scroll horizontaly to read the rest of the text, then your design is failing. I absolutely hate to have to do that as it’s not a common thing to do.

There are 2 problems with complex backgrounds:
1 – Longer loading times with more brandwidth taken. This can even cause the user to just give up on loading the website and move away.
2 – It distracts users and gives your website a more heavy feel to it you should avoid.

If you’re using a template or even when building a website by your own, make sure all the pages feel the same and not different websites. Imagine only one page has a specific search box. People don’t want to navigate through a lot of pages just to find which one has it!