At one time websites were designed to look good on laptops or desktops - that was how people accessed the internet.
Now your site could be viewed on a vast array of screen sizes, from something that fits in the palm of your hand, to a giant widescreen television.
How do modern websites cope?
Some people have two versions of their site, one for mobiles and one for desktops.
Google and the other major search engines recommend a different approach...
Responsive Web Design (RWD).
Websites that use RWD adjust the way they look according to the dimensions of the screen.
Desktop layouts may have generous space around the content to make it easy on the eye, where smartphone formats avoid wasting space.
Menu panels may be replaced with a menu button as the screen gets smaller, so you only see the menu items when you want to.
Mobile formats use smaller image files to save bandwidth, and images may even be omitted altogether if they are not absolutely necessary.
Items that change as the mouse hovers over them don’t work on a mobile. Your finger cannot be seen hovering, even when it is only millimeters above the screen.
Layouts change with screen size to avoid anyone having to scroll left to right. Scrolling up and down is fine.
One consequence of people browsing large websites on small screens is that they get very frustrated, very quickly if they can’t find what they want.
If someone is visiting your website, they probably need a tradesman like you, so they will want to contact you easily.
Mobile visitors don’t just want to find your phone number near the top of the page, they want to tap it to make the call.
Disappointed visitors tend to leave very quickly.
Google, Yahoo, and the other major search engines need to be popular to be successful.
This obviously involves showing relevant results for search queries, but things are more subtle than that.
If someone is searching from a mobile device, but the search engine keeps returning results that don’t work well on a mobile, they might consider switching search engines.
Your search ranking may not be as good on a smartphone as it is on a laptop/desktop, particularly if it only works well on the big screen.