Google crome provide easy way to check used or unused js and css.
Right Click + Inspect Element on the page, find the three dots on the far right (circled in image) and open Console Drawer (or hit Esc), finally click the three dots left side in the drawer (circled in image) to open Coverage tool.
Chrome launched a tool to see unused CSS and JS -...
Yes, search engines read it as "Hello World".
No, this won't harm your SEO efforts.
<span> has no semantic meaning it clearly won't change the weight of the word to the search engines.
No recommendation should be needed because there should be no difference. The <span> element has no semantic meaning whatsoever.
Every Language has its own syntax and structure and in html assignment is done using "=" and in css assignment is done using ":" .
but in css you can use : for selecting specific element from html
This css is ...