There are lots of different parts of web design which can negatively affect your conversions rate.
Using stock images
Stock images are a lazy way to fill image spaces on your site. The better websites use personalised photography and proffesionaly produced imagery instead of relying on cheap stock photos. Did you know that stock images can actually damage the credibility of your site too?
Overly large, high resolution images
Even if you are using your own images, it is silly to make them so large, or so high res that it takes an age for the site to load! It is trendy to have slider video clips in the header, but a fill screen video can end up taking up to 12 seconds to load – much, much slower than the maximum 3 seconds most people will wait!
It is important to think about how you place your call to actions on your site. If you have several all the same size, colour and postioning, it is difficult for the consumer to see which is the one you want them to click on. You need to make it easy for the customer, and guide them to click on the one you want them to!