How to eliminate errors on the site?

Very much need advice on how to eliminate errors that periodically occur on the site? I have recently started to create sites, so I do not know about all the nuances.

Of course, the beginner to understand it is not so easy. So it's better to learn about the experience of those who have long been engaged in the creation of sites. The easiest and fastest solution is to use the website error checker, which you will find on the website of this service https://pr-cy.io/ myself repeatedly encountered. If necessary, you can fix it all within a short time