When I check the html 5 Markup Validation Service I don't want to get these errors anymore:
Error Line 159, Column 51: Attribute name not allowed on element meta at this point.
<meta name="layout" content="main_profil"/>
Error Line 159, Column 51: Element meta is missing required attribute itemprop.
<meta name="layout" content="main_profil"/>
Is there anyway to solve this? I need this meta tag on top of the gsp to say which Layout will be used.
The error messages you are getting indicate that you have the <meta> element in the <body> section of your page, when it should be in the <head> section.
However, "layout" is not a valid name for the <meta> element in HTML5, so you're not going to be able to stop the validator from reporting an error for that.
You could try registering the "layout" name on the WHATWG wiki but it will take some time for the validator to catch up with that.