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I've been working on a premade packaged shopping cart website for a few months, and a lot of times when I've been trying to edit something, I have to use something like for example

div.myDiv
 { 
width: 400px !important;
}

To make it display as expected. Is this bad practice? Or is the !important command perfectly legal? Can this cause anything undesired further down the line?

Thanks :)

I've been working on a website for a few months, and a lot of times when I've been trying to edit something, I have to use !important, for example:

div.myDiv { 
    width: 400px !important;
}

in order to make it display as expected. Is this bad practice? Or is the !important command okay to use? Can this cause anything undesired further down the line?