Make sure your website is functional on different browsers and devices, also it is very important you do a speed analysis, no one likes a slow site. Once this is established, proceed to analyze your conversions rate per device, browser type, browser version and screen resolution. Use google analytics to find this data and then sort the devices/browsers by conversion rate, then search for high traffic and low conversion rate so you can look into this further. Use this tool to perform this hack, but be very careful because any small technical issue you make can result in huge losses of traffic, avoid this by following this checklist.