Also most of the older browsers, independent browsers and assistive technologies can not work well with frames. Again you might be excluding a portion of your intended viewers. Make column by column reading sensible. Summarize data presented in table form and use caption tags to help present the information. It is important to keep tables relatively simple when using them for page layout.
Assistive technologies read a table column by column.
If you have multiple overlapping columns you may make it very difficult to follow your page. Use evaluation tools and text-only browsers to verify accessibility and ease of use. Check all your pages and links once you have loaded them onto the server in their final resting-place. Use lab machines to check your pages. Do not use capital letters in your file names when creating your WebPages.