Steps to reproduce:

1. The sign-in page does not have a heading at all

2. On the browserwarning.php page, the first-order heading <h1> is missing

Further information:

Even if there is no requirement to mark the first and possibly only heading as a first-level heading with <h1>, this makes perfect sense and supports the logical heading structure. There are also good reasons for a heading in the login dialog, where there is no heading yet: 

1. Structural clarity: A headline helps to convey the structure and purpose of the dialogue programmatically.
2. Screen reader support: Clearly structured websites with correct headings are especially valuable for screen reader users because they can better understand the hierarchy and context of the page.
3. Semantic coherence: An appropriate headline contributes to semantic coherence, which is important for assistive technologies.
4. Navigation aid: A headline can serve as a landmark, especially if users want to jump straight to the main content.

Solution:

• For the login page: The page should contain a heading <h1> whose text suggests how users can interact on the page. For the login page, the text could be short and friendly, 'Please log in' or Log in to Zabbix. 

• For the page browserwarning.php: <h2> heading can be changed to <h1>.