You also need to design your pages for content . For example, you could add color to certain portions of text or you can highlight certain words with color to make them stand out. In your browser, it may look great. However, many people still use browsers that do not support coloring portions of text. So while it looks great in your browser, it will not give the same looks in other browsers, and text that you thought were highlighted by color will not be highlighted in these other browsers.
Color is used to change the appearance of text.
If a browser can't perform the appearance change, it has no way to determine an alternative. As a result the color attribute is simply ignored. Also, you may be able to fit a heading neatly on one line in your browser while in another browser, the font size could be a little bigger and the heading will not fit on one line. Or the reverse could be true, a heading may not fit on one line in your browser, but in another browser with a little smaller font size, it will fit into one line. Thus the appearance of the heading in your browser could be different in another browser.