Question: I'm working on sending emails to various email clients(such as yahoo,hotmail,gmail,....). 

I have a div with id `OrderInfo` inside that I have a **variable** which generates a dynamic table.

**HTML**

```
<div id="OrderInfo">
  variable 
</div>

```

The dynamic **table** generates headers(`th`) with lower case, so I want to change that to uppercase and few more styling. So I have written a selectors

**CSS**

```css
#OrderInfo table tr th {
  text-transform: uppercase;
  background-color: #737373;
  color: white;
}

```

This is working fine for yahoo, hotmail but not for **gmail**.

I came across that only inline styles work for gmail but how can I the styles of modify a dynamic one.

I have no control on the **variable** (I mentioned in the div) it generates a table with values which processes while sending to the client.

So I cannot keep a static table and cannot change the way it renders

Answer: 
**gmail** as well as some other web and desktop/mobile clients strips away css stylesheets either imported or embedded in a `<style>...</style>` node in the `head`

Put them inline:

```
<div id="OrderInfo">
    <table>
        <tr>
            <td style="text-transform: uppercase; background-color: #737373; color: white;">
                <!-- .......... -->
            </td>
        </tr>
    </table>
</div>

```

As a more general advice: building email html is not trivial as final result may vary a lot depending on the recipent's mail client.

The general rule is to make the **html** as simple as possible, avoiding "modern" css features; use nested tables instead of divs when possible (some says build the html as if you were building a 15 years ago webpage).

The above is very general and may not be always true.

There are several resources online that gives advices and rules on how to make an html email or template.

Finally the only and one rule to always follow if you want to be sure of the result: **test your messages with various client**
UPDATE 2018
-----------

GMAIL now and from a while ago has been supporting embedded CSS, so you can use CSS inside tag `<style>` in `head`, it even allow/supports the use of media queries.

---

**OLD ANSWER**

Gmail doesn't support embedded CSS, you need to use inline styles, take a look at this

[12 Things you MUST Know when Developing Emails for Gmail and Gmail Mobile Apps](https://www.emailonacid.com/blog/article/email-development/12_things_you_must_know_when_developing_for_gmail_and_gmail_mobile_apps)

Here is what you could do:

`<th bgcolor="#737373" style="text-transform: uppercase; color:white></th>`