CSS or Cascading Style Sheets makes life easy for you.

The Bright Side

• It is possible to avoid the cascade by writing all the CSS rules inline. That would be painful, and even more painful if you were to revise the site. It is possible to embed styles in the head of the HTML document. This is great for writing a style definition once, and applying it many times throughout the page. If there is more than one page, however, it is better to separate the styles out of the document into an external style sheet. A link in the head to that stylesheet keeps all the pages synched to the same style definitions. Imagine updating your whole site by changing only one rule. That is the power of CSS!
• Using a single stylesheet is a boon for consistency.
• A reduction in file size.
• By separating form from content, the content can be repurposed so it works on iPhones, tablets and computer screens. This is called responsive web design.
• Build fantastically complex web pages with relative ease.
• Ease of making changes to the layout.
• CSS allows for better Search Engine Optimization. You can put the most important info first no matter where it is on the page. Content remains readable compared to using tables for layout purposes.

The Darker Side

• The cascade can become confusing as the number of style definitions grow.
• Forget one character and the whole thing can break down. More usually, only the declaration breaks down, but watch out for errors.
• Primitive layout tools (update is in progress but not yet ready for prime time).
• Implementation in different browsers are similar, but not necessarily the same.
• The latest and the greatest features are not always supported by all the browsers.
• Internet Explorer 6.5 hell.