You may already notice that some pages on Safari that won’t let you scroll down. This is primarily due to the fact that the web site you are visiting has some poorly designed design elements (CSS, HTML 5, JavaScript etc.), thus Safari cannot render them properly. To overcome this issue, try this:
Disable JavaScript in Safari by tapping tap Settings > Safari.
This will probably fix your problem but since now you’ve now turned JavaScript off, many other web sites that require JavaScript will not work properly in Safari. Thus, you may want to turn JavaScript back on after you are done with the web page.
Related: Safari on iPad / iPod / iPhone with websites containing frames