This small but effective article is both for usability veterans and people new to Web usability and CSS.
P.S: I don’t want see anymore table-coded websites on the Web.
CSS makes HTML pages smaller in file size, thereby speeding page download times.
World Wide Web Consortium (W3C) Recommendation
CSS is one of the W3C’s core recommendations, so your CSS-styled site will comply with the current standards. Moreover, most HTML formatting tags are being deprecated by older browsers and aren’t even supported in XHTML code, so you have no good reason not to use CSS for most, if not all, of your content styling and positioning needs.
Easy To Edit
CSS is infinitely editable, giving you the flexibility of changing the look of your pages as often as you like without ever altering the content.
Easy To Control
CSS helps separate presentation (how the page looks) from content (what’s on the page) by moving all the page-styling instructions into a centralized location. That location can either be in-line with the code or internal in the head area of the Web page, or in an external CSS document to which all the pages on a site are linked, the latter being the most useful method for working with CSS. The benefit of having an entire site’s style information contained in a single external CSS file is that doing so allows for instant site-wide style updates.
Always Will Be Trend
CSS styles your content semantically, which means that it requires fewer styles than the old HTML formatting tags. For example, CSS allows designers to redefine the presentation of content contained inside particular tags, such as automatically adding a particular color and font face to any content marked up with H3 tags or applying the same background color and border attributes to any tables on the site.
No Need For Extra Codes
CSS can be used to style the look of text, images, and objects as well as to position objects on a Web page. This feature alone drastically reduces the amount of code required to display objects on a page. For instance, objects contained in div tags can be absolutely positioned on a page with CSS. Before, to place something in an exact spot on a page required code hacks involving the use of tables with empty table cells and spacer gifs. All that extra code goes away with CSS.
Easy To Update
CSS is a more affordable solution for styling content because it takes less time to implement and update than the older styling techniques did. With the old way, even simple changes might require the hand-editing of all the individual pages on a site. With CSS, one change there can update a style across an entire Web site.
After you begin styling your content with external CSS, you’ll probably never want to go back to using the old tags for styling.
W3C Web Style Sheets — http://www.w3.org/Style
W3C Schools — http://www.w3schools.com/Css
HTML and CSS Tutorials. And Stuff — http://htmldog.com
A List Apart — http://www.alistapart.com/topics/code/css
CSS Dog — http://cssdog.com
Recent CSS Bookmarks on Delicious — http://delicious.com/tag/css
SitePoint CSS Reference — http://reference.sitepoint.com/css
The Web Standards Project — http://www.webstandards.org/learn
Source : http://www.merttol.com/articles/css/7-benefits-to-learn-and-use-css.html