Arduino + ESP8266 as Webserver
Are you using an arduino (as in UNO / mini / nano etc.) and communicating with a separate esp8266 via serial?
I've found esp8266 module to be more reliable by using a 12e or such like and running arduino boot loader on it. There's more memory to play with, and I tend to formulate the data I need within the ESP8266 and then communicate with that via serial or I2C to get data / requests to and from. 

Make sure you're supplying the ESP module with enough current - they're juicy little things, so good 300mA @3.3v and use a good 470uf 10v cap or something too.. They can splurge current on occasion, particularly when scanning networks. 

Let me know what set up you're running 

Cheers