lait on "W3 finds a lot of validation errors"

W3 Validator (https://validator.w3.org/) finds a lot of errors for http://la-itconsultancy.co.uk. I cannot do anything about them, because when I go to my theme, I simply cannot see the error. For example, the W3 validator said that my icon11 image has alt attrubute , but it doesn't have it in the dashboard.
I wrote the alt attribute manually. Can W3 misinterpret somethings?