While CSS syntax is pretty straightforward, it has some common pitfalls, especially if you've gotten used to writing HTML or XHTML.
To check the easy stuff with CSS:
Make sure you separate your properties from their values with a colon (:) not an equals sign, like you do in (X)HTML (Figures 22.8 and 22.9).
Figure 22.8. Bad! It's hard to break the habit of separating properties and values with the equals sign. But you must.
Figure 22.9. Much better. Always use a colon between the property and the value. Note that it doesn't matter if you add extra spaces before and after the colon.
Be sure to complete each property-value pair with a semicolon (;). Make sure there are no extra semicolons (Figures 22.10 and 22.11).
Figure 22.10. Bad! You must put one and only one semicolon between each property-value pair. Here there's one missing and one extra.
Figure 22.11. One way to make sure that each property-value pair is separated by the next with a semicolon is to give each one its own line. It's easier to see the semicolons when they're not in a sea of properties, values, and colons.
Don't add spaces between numbers and their units (Figures 22.12 and 22.13).
Figure 22.12. Bad! Never put spaces between the number and the unit.
Figure 22.13. This will work. Note that the spaces between the colon and the value are optional.
Don't forget to close your brackets.
Don't quote valuesas you do in (X)HTML. The only values that have quotes in CSS are multiword font names.
Make sure you're using an accepted value. Something like font-style: none isn't going to work since the "none" value is called normal. You can find a complete list of CSS properties and values in Appendix B, CSS Properties and Values.
Don't forget the closing </style> tag with internal style sheets (see page 131).
Make sure you've linked the (X)HTML document to the proper CSS file, and that the URL points to the desired file. URLs are relative to the CSS file, not to the (X)HTML file (see page 129).
Watch the spaces and punctuation between the selectors.
Make sure the browser supports what you're trying to do (see page 350). Support for CSS varies.