These features are currently available in version 1.3 of WEXTOR:

• complete and incomplete experimental designs
• experimental (between-subjects and within-subject) factors
• quasi-experimental (natural) factors
• automatic avoidance of page number confounding
• Javascript test redirect functionality to minimize drop-out
• randomized distribution of participants to experimental conditions
• distribution of participants to experimental conditions based on levels of quasi-experimental factors
• random or fixed order of blocks
• automatic avoidance of frequently made configuration errors when naming experimental conditions in Web experimenting
• randomly generated continuous user IDs for enhanced multiple submission control
• optional client-side response time measurement
• implementation of the warm-up technique for drop-out control
• interactive dependent measures and materials (created via content wizard)
• generation of ready-to-copy HTML and Javascript code
• visual display and listing of experimental design, in terms of directories (folders) and Web pages

... and WEXTOR is based on six years of experience with Web experimenting. It will not generate experimental ideas for you (yet ;-)