It appears because the CSS is found twice in the file.
crossed out
lines means, that those styles were found but have been overwritten.
To put simply, display:block like console means that the CSS was applied but then some more relevant CSS is found and overwrote the current one.
So for example, if you have markup like :
<html>
<head>
<style>
h2#title{color : red}
h2#title{color : yellow}
</style>
</head>
<body>
<h2 id="title"> Hi </h2>
</body>
</html>
then, since h2#title
is found twice in the file, only one can be applied, so, you will see something like this, whichever got overwrote would be crossed :
h2#title{
color : red
}
A Good Read on this : https://developer.chrome.com/devtools/docs/elements-styles?csw=1&safe=on#computed_style
Related Helpful Thread : Chrome Developer Tools: How to find out what is overriding a CSS rule?