If you are a member of a trade association or are registered with a regulator you may be able to display their logo on your website.
In some cases you may be required to do so as a condition of membership. Any such use will more than likely be controlled by a ‘license’. In other words as the logo will be copyright and may be a registered Trademark the owner will permit you to use it in certain circumstances. The detail will be included in an agreement and it is important that you follow the terms of the agreement otherwise you could prejudice your membership of the organisation.