Understanding the order of CSS rules is crucial:
#main > div{
color: red;
}
#main > div{ /*last defined rule*/
color: blue; /*will override*/
}
Let's address your main question:
Using !important
can be useful in certain situations. Refer to this code from a comment on css-tricks by Marco Campos:
I used it in a specific scenario to fix an overflow issue in IE9 while keeping other browsers intact. Despite recommending browser upgrade, I had to use !important for proper rendering in IE9.
body {
overflow:auto !important; /* for all other browsers, the !important is for IE9 */
overflow:hidden\9; /* for IE<9 */
}
Now, let's delve into how CSS selectors operate:
The style system prioritizes matching rules starting with the key selector, then moving leftward (checking ancestors in the selector). The faster resolution results from minimal rule checks required for each element.
For instance, an element with an ID only checks ID rules and so forth. Universal Rules are always scanned.
Hence, using #main > #child
is less efficient than just #child
. Avoid the former for better performance.
Consider utilizing parent element selectors for overrides without !important
:
body #child{
color: purple !important;
}
An alternative approach without multiple id selectors or !important
:
body div#child{
color: blue; /*will override*/
}
A simpler solution involves classes:
.parent-class #child{
color: blue; /* will take precedence*/
}
#main > div{
color: red;
}
Note: Avoid using !important
in inline styles as it hinders overrides.
<div style="color: blue !important;">color is always blue</div>
In the dilemma between #main > #child{color: blue;}
and #child{color: blue !important;}
, prioritize the latter for ease of override and better efficiency.