1) Backup & Copy site files & database to a Local Site and/or Staging Server, including .htaccess, robots.txt, sites directory (settings.php), contrib modules, custom theme, & files directory. Setup a "Legacy" version of the site to reference original config settings and content without disturbing the live site. Setup a "Working" version in which to perform upgrade.

2) Perform a Module Audit and create a spreadsheet of the audit for the for the site. This will become a useful reference document for the site to help note which modules may have been orphaned, replaced, etc.

Title Element

The page title element (some refer to it as the title tag which is incorrect) is one of the most important factors for ranking highly in the search engines.

Page title elements are normally 3-9 words (60-80 characters) maximum in length, no fluff, straight and to the point. This is what shows up in most search engine results as a link back to your page.

Make sure your Page Title Element (title tag) is relevant to the content on the page.

References
* W3C - 7.4.2 The TITLE element

Designing an HTML email that renders consistently across the major email clients can be very tedious and time consuming. Support for even simple CSS varies considerably between email clients, and even different versions of the same client. Here is a checklist to compare what CSS styles are allowed by various email browsers such as Outlook, Yahoo, Hotmail, Apple iPhone, Gmail, Lotus, & AOL.

To display text within a form field and have that text disappear when a user clicks inside the field, add one of the following scripts to the element:

Example 1:
<input onfocus="this.value=''" type="text" value="some text" />

Example 2:
<input onfocus="this.select()" type="text" value="some text" />

There are times when browsers render CSS and HTML differently depending on the platform and browser being used. Usually, I can check for cross-browser consistency using only Windows and variety of installed browsers for Windows (Internet Explorer, FireFox, Safari, Google Chrome, etc.). However, there is sometimes major differences in how the PC version of a browser renders a page v/s the Mac version of a particular browser. I have noticed this most in Safari between Windows and Mac.

The following PHP function checks to see if a particular taxonomy id (term name) exists:

<?php
if(!empty($node->taxonomy) && $node->taxonomy[6]-->name == 'Term-name-here'){
print 'Term exists';
}else{
print 'Term does not exist';
}
?>

Windows Automatic Updates - what a pain!
Often with unexpected results.

To disable Windows Automatic Updates in Windows XP, do the following:
1) Open the "Start" menu
2) Go into "Control Panels"
3) Open "System"
4) Click the "Automatic Updates" tab
5) Select the "Turn Off Automatic Updates" option

The following PHP script checks to see if a url argument is TRUE:

<?php
if($_SERVER["REQUEST_URI"] == '/contact'){
print 'Contact';
}else{
print '';
}
?>

Here is a list of available variables within page.tpl for Drupal 6:

General utility variables:
$base_path: The base URL path of the Drupal installation. At the very least, this will always default to /.
$css: An array of CSS files for the current page.
$directory: The directory the theme is located in, e.g. themes/garland or themes/garland/minelli.
$is_front: TRUE if the current page is the front page. Used to toggle the mission statement.
$logged_in: TRUE if the user is registered and signed in.