Professional websites separate styling from content. There are many reasons for this, the most obvious (to a developer) being the ability to control the appearance of many pages by changing one file.
Style information is coded in CSS, cascading style script, and usually stored in files with the suffix .css. A webpage contains a link to the associated .css file so a browser can find the appropriate style information to apply to the page. CSS can also be placed inside a html file between <script></script> tags.
All CSS code is applied to an element of the html/xml page. If you want a style to encompass a whole page, you would probably apply it to the <body> element. You can apply styles to any html element such as <p>, <table> or <div> elements. To style a particular element it needs to have an ID. For example, to apply styles to the <div> containing the title, you would first include an ID in the html - <div ID="title">.