Could a CSS file update on my site hurt rankings?

[serenoo]

My website is the number one for one keyword. I want to improve the graphic of my website, so I would change the css file, but I will not touch the php files of the website.
Could the update of the css file hurt my ranking on Google?

[tedster]

I really doubt it - unless, of course your CSS update causes hidden content that the visitor cannot reveal through a click or hover event.

Google does do some visual page simulation, so if your CSS change moves blocks of content into different page positions, that theoretically might make some ranking difference. But I've never seen or heard of it happening.

[serenoo]

Good. If I change the php page adding only the class tag, will that could cause a problem?
For example:
I have on a php page
<table>
and I will replace it with
<table class="red">

[tedster]

I've never seen a problem with that kind of change in the source code.