When having a website designed, it is vital to think in detail about the layout of the site. You need the design to be clear and easy for the viewer to navigate round different areas of the site. Each page should have a call to action to entice the viewer to interact either by completing a sale or making an enquiry.
Once your site is ready to go live you need to thoroughly test it. This means going through every page and checking all the images are loading, links are clicking through to the right place and content is all correct in terms of spelling and grammar. You should also test any enquiry forms you have on the site and if it is e-commerce, then complete a test purchase.
Once you are happy that the site is working ok, it is always worth asking someone else to have a look over it that has not been involved in the project much as sometimes you can be too close to it to notice simple mistakes.