Cant apply CSS style - php

Question

Ive been trying to increase the font size for the TH tag via the css style sheet:
th {
color:#D5DDE5;
background:#1b1e24;
border-bottom:4px solid #9ea7af;
border-right: 1px solid #343a45;
font-size:23px;
font-weight: 100;
padding:24px;
text-align:left;
text-shadow: 0 1px 1px rgba(0, 0, 0, 0.1);
vertical-align:middle;
}
for the following code:
<?php
include ('connect-mysql.php');
$sqlget="SELECT * FROM data ORDER BY score desc LIMIT 10";
$sqldata= mysqli_query($conn, $sqlget);
echo "<table width='1500'>";
echo "<tr>";
echo "<th>Position</th>";
echo "<th>First Name</th>";
echo "<th>Last Name</th>";
echo "<th>Score</th>";
echo "</tr>";
$counter = 1;
while($row = mysqli_fetch_array($sqldata, MYSQLI_ASSOC)) {
echo "<tr><td width='5%'>";
echo "<b>".$counter."</b>";
echo "</td><td>";
echo "<div style='font-size:40px'>";
echo "<b>".$row['firstName']."</b>";
echo "</div>";
echo "</td><td>";
echo "<div style='font-size:40px'>";
echo "<b>".$row['lastName']."</b>";
echo "</div>";
echo "</td><td width='20%'>";
echo "<b>".$row['score']."</b>";
echo "</td></tr>";
$counter++;
}
echo "</table>";
?>
As you can see i have been using inline css styles as the external style sheet seems to have jammed, i would like to increase the font size of the TH tags but there is no response when changing 'font-size:23px'
What am i doing wrong ?

Answer 1

Try to change font-size in the browser development panel.
It will show you if there are some other css instructions that overwrites yours (or any other reason).

Answer 2

Thanks for this I managed to get it to work using kunals help.
echo "<th style='font-size:2.0em'>Position</th>";
using "" instead of ''inside the th tag causes php errors for me.
using px caused formatting issues so i used em
I am still wondering why my CSS style sheet isnt working :/

Answer 3

Make it like this, and you're done...
echo "<table width='1500'>";
echo "<tr>";
echo "<th style="font-size:23px;">Position</th>";
echo "<th style="font-size:23px;">First Name</th>";
echo "<th style="font-size:23px;">Last Name</th>";
echo "<th style="font-size:23px;">Score</th>";
echo "</tr>";
add inline css to th tags...