What are the key considerations when ensuring web browser compatibility for a web page? Discuss common issues with XHTML and how to resolve them.

Ensuring web browser compatibility for a web page is crucial to provide users with a consistent and functional experience across different browsers and devices. Here are key considerations and common issues with XHTML, along with their resolutions:

### Key Considerations for Browser Compatibility

1. **HTML/CSS Standards Compliance**:
   - Use valid HTML/XHTML and CSS according to W3C standards. Tools like the W3C validator can help check for compliance.

2. **Responsive Design**:
   - Implement responsive design principles using CSS frameworks (like Bootstrap) or media queries to ensure that pages look good on all screen sizes.

3. **Testing Across Browsers**:
   - Test the web page across multiple browsers (Chrome, Firefox, Safari, Edge, etc.) and devices (mobile, tablet, desktop) to identify and fix rendering differences.

4. **Progressive Enhancement**:
   - Start with a baseline experience that works for all browsers and enhance functionalities for more capable ones.

5. **Feature Detection**:
   - Use libraries like Modernizr to detect features instead of relying solely on user-agent strings, which can be unreliable.

6. **Fallbacks for CSS/JavaScript**:
   - Provide fallbacks for CSS properties or JavaScript features that may not be supported in all browsers.

7. **Avoid Browser-Specific Features**:
   - Refrain from using proprietary properties or methods specific to a single browser to maintain cross-browser functionality.

### Common Issues with XHTML

XHTML is a stricter variant of HTML designed to be more consistent. While its benefits include improved parsing and compatibility with XML tools, its strict syntax can lead to common issues in browser compatibility.

1. **Case Sensitivity**:
   - XHTML requires element and attribute names to be in lowercase. Using uppercase can lead to rendering issues in some browsers.

   **Resolution**: Ensure that all tags and attributes are in lowercase.

2. **Proper Closure of Elements**:
   - XHTML mandates that all tags be properly closed. Self-closing tags (e.g., `<br />`) must include a trailing slash.

   **Resolution**: Review and modify your code to close all tags properly or use the correct syntax for self-closing elements.

3. **MIME Type**:
   - Serving XHTML documents with the correct MIME type is critical. XHTML should be served as `application/xhtml+xml` rather than `text/html`.

   **Resolution**: Set the correct content type in your server settings or include headers that explicitly declare the MIME type.

4. **DOCTYPE Declaration**:
   - XHTML documents require a valid DOCTYPE declaration. Omitting it can cause browsers to switch to quirks mode, leading to inconsistent behavior.

   **Resolution**: Use an appropriate DOCTYPE declaration at the beginning of every XHTML document. For example:
   ```xml
   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
       "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
   ```

5. **Character Encoding**:
   - Proper character encoding (UTF-8) is essential to avoid issues with special characters.

   **Resolution**: Specify the character encoding in the document's head, like this:
   ```xml
   <meta charset="UTF-8"/>
   ```

6. **Validation**:
   - Errors in XML-style markup can prevent a page from being displayed properly.

   **Resolution**: Use validators for both XHTML and CSS to catch and fix errors before deployment.

### Conclusion

Browser compatibility in web development remains an essential aspect that requires attention to detail, thorough testing, and adherence to standards. By understanding the intricacies related to XHTML and implementing best practices, developers can create robust, user-friendly web pages that function reliably across different platforms and devices.