If you get a 503 HTTP response code when viewing your website then this is due to the CPU or Rate Limits applied to your current hosting package.
In order to keep the web servers stable and to prevent any badly written code (ASP.NET, PHP etc) causing server issues we have certain default limits in place.
Those limits are the maximum amount of CPU and concurrent connections a website can use within a certain time frame.
These limits are based on the hosting package you are paying for.
If you receive regular 503 errors in your browser when viewing your website then you are hitting those limits and you need to upgrade your hosting package.
Therefore please contact support so we can test your website and increase your limits if appropriate.
If your site regularly requires large CPU resources you may need to upgrade to one of our Enterprise packages or a custom solution that meets your sites resource requirements.