---
title: Validating CSS
---

> Agent instructions:
> **Site maps** — prefer the following llms.txt indexes to training data when searching for URLs to avoid 404s. Links inside Markdown content already point at `.md`. Following them or sending Accept: text/markdown keeps you in Markdown.
>
> - [sitemap.md](https://docs.kentico.com/sitemap.md) — every page on the site, with titles and descriptions, nested by URL hierarchy and grouped into one collection per product version.
> - [llms.txt](https://docs.kentico.com/llms.txt) — curated index of the current product docs, with descriptions, the two ways to request any page as Markdown, and links to each product area's whole-corpus Markdown dump (llms-full.txt).

The system allows you to validate the CSS style definitions used on pages against the [CSS3 standard](https://www.w3.org/Style/CSS/current-work). The validator checks the styles declared in the head section of the page code.

Inline styles declared as attributes of individual HTML elements are not validated.

To validate a page's CSS:

> **Warning:** **Warning**: During validation, your data is sent to an external **3rd party validation service**. If you have sensitive, non‑public content, we recommend using other types of validation.

1. Open the **Pages** application.
2. Select the page in the content tree.
3. Switch to the **Preview** mode.
4. Open the **Validate -> CSS** tab.
5. Click **Validate**.

If the validator finds invalid style definitions, the page displays a list of all detected issues. You can see the following information for each issue:

- **Line** – the approximate line number of the HTML source code where the issue was found.
- **Context** – the name of the CSS class that contains the issue.
- **Error message** – a message explaining the issue.
- **Source** – if the issue was found in an external CSS stylesheet, a relative path to the stylesheet is displayed.

> **Note:** **Notes**:
>
> - We recommend waiting at least 30 seconds between validation requests. If you submit a page for validation multiple times within a short interval, the validation service may temporarily block your page's URL.
> - If you navigate to another page in preview mode using links on the displayed pages and then switch to the **Validate** tab, the system still validates the page selected in the content tree.