Tables — Perhaps one of the most common and useful constructs in Web design. Since early versions of HTML had few page layout controls, tables emerged as a popular way to exert some control over how objects were displayed in the browser window. Although originally intended as a mechanism for displaying tabular data, tables are commonly used to achieve other typographical effects, such as establishing margins or creating multiple columns of text.
Forms — It looks more professional when you allow your visitors to fill in information right on your page rather than using a "mailto:" command. A form does basically what email does — it sends information. Text boxes and areas, radio buttons, check boxes, drop-downs, pop-ups; these varied types of forms then use the reset or submit button to transmit the values. But forms are more versatile than email. They can be used for creating polls for your visitors, collecting demographic or other characteristic information for relational databases, or as a security device for account login.
Frames — In HTML, frames give designers the ability to display multiple pages of content in a single screen. This powerful capability is also one of the most controversial HTML practices and a constant topic of heated discussion among designers. Here's a quick refresher on how to create HTML frames, including an explanation of the related tags, some common applications, and some concerns about using them. On the plus side, navigation methods such as menus, bars, remote controls, or even DHTML hierarchy can remain static in a single frame that never changes. The biggest concern with frames is the difficulty search engines have indexing the content from framed pages.
Cascading Style Sheets — CSS is a technology that gives web authors enhanced control over the look of elements in a web page. Things once considered unchangeable, such as the underline beneath links, the color of form elements, the spacing between text, and more, can now all be altered, thanks to CSS. Style sheets come in multiple levels and hierarchies. They can operate on a single individual HTML tag, on all occurances of a tag on a page, or through external style sheets, on all occurances of a tag within your web site.