A website needs to follow a few simple rules of human computer interaction design (HCID) for effective on-line marketing:

Easy navigation – the visitor must quickly be able to see what to do, how to find your products, how to get to the check-out and how to pay.

Clear images – a picture is worth a thousand words but only if it is of good quality and relevant.

Good use of colour – bright garish colours can put people off.  Your website is a reflection of your company image.

Keep it simple – every element of the page should help your visitor make a purchase not distract them.

For help with designing a new website or upgrading your existing site you should consult, web design Salisbury they offer profesional web design and Search Engine Optimisation and are based in the UK.