Most websites make use of what is called 'CSS'. 'CSS' is short for 'Cascading Style Sheet' and is a text document that defines the rules for the design of the website, such as background images, positions of layers and the various font types. By utilising 'CSS' documents, a developer can easily change all of the font sizes / colours, background images and overall website design by simply changing a few lines on the CSS document for the website rather than editing the format for every page on the website.
This can be particularly beneficial when you want to have a website that has large number of images for a standard web browser while making the website smaller and narrower for a mobile device.
Many CMS and CRM websites include some very clever technologies that can allow for easy styling on a per page basis, which can provide you with a range of webpage layouts and formats while also maintaining your company image and colour schemes.
Website themes can also be manipulated to suit a particular event, such as a sporting event or cultural event that ties in with you business or appeals to your primary target market.