This guideline states that the default human language of web pages should be identified in the markup. The problem is that users with cognitive disabilities may struggle to understand the content of a webpage if the language is not identified. The recommended solution is to specify the language of the webpage in the HTML code, allowing assistive technologies to provide accurate language support to users with cognitive disabilities.

Rephrase this sentence in 9th grade, make it 3 sentences long.

It's important to indicate the main language used on a webpage. If the language isn't specified, people with cognitive disabilities might find it hard to understand the content. To help, specify the webpage's language in the HTML code so assistive tools can provide accurate language support.