moved error styles in css file

public/index.html

@@ -45,7 +45,7 @@
             <div>
               <textarea oninput="handleTextAreaChange()" placeholder="Enter text here..." class="box-input"
                 name="textarea" id="manual-text-entry" cols="90" rows="5" value=""></textarea>
-              <div id="textarea-validation" style="color: red;display: none;">Please enter text.</div>
+              <div id="textarea-validation" class="error-message">Please enter the text.</div>
             </div>
             <div>
               <label for="calculatedTextCharacters">Total characters in text: </label>
@@ -57,7 +57,7 @@
             <label for="inputTextCharacters">Enter number of characters: </label>
             <input oninput="handleCharacterInputChange()" placeholder="e.g. 120" class="box-input" type="number"
               id="inputTextCharacters" name="inputTextCharacters" value="">
-            <div id="textCharacters-validation" style="color: red;display: none;">Please enter number of characters.</div>
+            <div id="textCharacters-validation" class="error-message">Please enter number the of characters.</div>
           </div>
         </div>
         <div>
@@ -69,7 +69,7 @@
             <option value="Third Year">Third Year</option>
             <option value="Fourth Year">Fourth Year</option>
           </select>
-          <div id="readerLevel-validation" style="color: red;display: none;">Please select reader level.</div>
+          <div id="readerLevel-validation" class="error-message">Please select the reader level.</div>
         </div>
         <div>
           <label for="readerCategory">Reader Category:</label>
@@ -80,7 +80,7 @@
             <option value="Good-ability group">Good-ability group</option>
             <option value="Average-ability group">Average-ability group</option>
           </select>
-          <div id="readerCategory-validation" style="color: red;display: none;">Please select reader category.</div>
+          <div id="readerCategory-validation" class="error-message">Please select the reader category.</div>
         </div>
         <div>
           <div>